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Sample records for calcium release channel

  1. Computational study of a calcium release-activated calcium channel

    Science.gov (United States)

    Talukdar, Keka; Shantappa, Anil

    2016-05-01

    The naturally occurring proteins that form hole in membrane are commonly known as ion channels. They play multiple roles in many important biological processes. Deletion or alteration of these channels often leads to serious problems in the physiological processes as it controls the flow of ions through it. The proper maintenance of the flow of ions, in turn, is required for normal health. Here we have investigated the behavior of a calcium release-activated calcium ion channel with pdb entry 4HKR in Drosophila Melanogaster. The equilibrium energy as well as molecular dynamics simulation is performed first. The protein is subjected to molecular dynamics simulation to find their energy minimized value. Simulation of the protein in the environment of water and ions has given us important results too. The solvation energy is also found using Charmm potential.

  2. Inhibition of parathyroid hormone release by maitotoxin, a calcium channel activator

    International Nuclear Information System (INIS)

    Maitotoxin, a toxin derived from a marine dinoflagellate, is a potent activator of voltage-sensitive calcium channels. To further test the hypothesis that inhibition of PTH secretion by calcium is mediated via a calcium channel we studied the effect of maitotoxin on dispersed bovine parathyroid cells. Maitotoxin inhibited PTH release in a dose-dependent fashion, and inhibition was maximal at 1 ng/ml. Chelation of extracellular calcium by EGTA blocked the inhibition of PTH by maitotoxin. Maitotoxin enhanced the effects of the dihydropyridine calcium channel agonist (+)202-791 and increased the rate of radiocalcium uptake in parathyroid cells. Pertussis toxin, which ADP-ribosylates and inactivates a guanine nucleotide regulatory protein that interacts with calcium channels in the parathyroid cell, did not affect the inhibition of PTH secretion by maitotoxin. Maitotoxin, by its action on calcium channels allows entry of extracellular calcium and inhibits PTH release. Our results suggest that calcium channels are involved in the release of PTH. Inhibition of PTH release by maitotoxin is not sensitive to pertussis toxin, suggesting that maitotoxin may act distal to the site interacting with a guanine nucleotide regulatory protein, or maitotoxin could interact with other ions or second messengers to inhibit PTH release

  3. Sarcoplasmic Reticulum Calcium Release Channels in Ventricles of Older Adult Hamsters

    Science.gov (United States)

    Nicholl, Peter A.; Howlett, Susan E.

    2006-01-01

    Whether the density of sarcoplasmic reticulum (SR) calcium release channels/ryanodine receptors in the heart declines with age is not clear. We investigated age-related changes in the density of [3H]-ryanodine receptors in crude ventricular homogenates, which contained all ligand binding sites in heart and in isolated junctional SR membranes.…

  4. Maitotoxin: Effects on calcium channels, phosphoinositide breakdown, and arachidonate release in pheochromocytoma PC12 cells

    International Nuclear Information System (INIS)

    Maitotoxin (MTX) increases formation of [3H]inositol phosphates from phosphoinositides and release of [3H]arachidonic acid from phospholipids in pheochromocytoma PC12 cells. Formation of [3H]inositol phosphates is detected within 1 min of incubation even with concentrations as low as 0.3 ng/ml (90 pm) MTX, whereas release of [3H]arachidonic acid is not detected until 20 min even with concentrations as high as 1 ng/ml (300 pm) MTX. Stimulation of arachidonic acid release can be detected at 0.03 ng/ml (9 pm) MTX, whereas 0.1 ng/ml (30 pm) MTX is the threshold for detection of phosphoinositide breakdown. Organic and inorganic calcium channel blockers, except Cd2+ and a high concentration of Mn2+, have no effect on MTX-elicited phosphoinositide breakdown, whereas inorganic blockers (e.g., Co2+, Mn2+, Cd2+), but not organic blockers (nifedipine, verapamil, diltiazem), inhibit MTX-stimulated arachidonic acid release. All calcium channel blockers, however, inhibited MTX-elicited influx of 45Ca2+ and the MTX-elicited increase in internal Ca2+ measured with fura-2 was markedly reduced by nifedipine. MTX-elicited phosphoinositide breakdown and arachidonic acid release are abolished or reduced, respectively, in the absence of extracellular calcium plus chelating agent. The calcium ionophore A23187 has little or no effect alone but, in combination with MTX, A23187 inhibits MTX-elicited phosphoinositide breakdown and enhances arachidonic acid release, the latter even in the absence of extracellular calcium. The results suggest that different sites and/or mechanisms are involved in stimulation of calcium influx, breakdown of phosphoinositides, and release of arachidonic acid by MTX

  5. Calcium Occupancy of N-terminal Sites within Calmodulin Induces Inhibition of the Ryanodine Receptor Calcium Release Channel

    Energy Technology Data Exchange (ETDEWEB)

    Boschek, Curt B; Jones, Terry E; Squier, Thomas C; Bigelow, Diana J

    2007-08-01

    Calmodulin (CaM) regulates calcium release from intracellular stores in skeletal muscle through its association with the ryanodine receptor (RyR1) calcium release channel, where CaM association enhances channel opening at resting calcium levels and its closing at micromolar calcium levels associated with muscle contraction. A high-affinity CaM-binding sequence (RyRp) has been identified in RyR1, which corresponds to a 30-residue sequence (i.e., K3614 – N3643) located within the central portion of the primary sequence. However, it is currently unclear whether the identified CaM-binding sequence a) senses calcium over the physiological range of calcium-concentrations associated with RyR1 regulation or b) plays a structural role unrelated to the calcium-dependent modulation of RyR1 function. Therefore, we have measured the calcium-dependent activation of the individual domains of CaM in association with RyRp and their relationship to the CaM-dependent regulation of RyR1. These measurements utilize an engineered CaM, permitting the site-specific incorporation of N-(1-pyrene) maleimide at either T34C (PyN-CaM) or T110C (PyC-CaM) in the N- and C-domains, respectively. Consistent with prior measurements, we observe a high-affinity association between both apo- and calcium-activated CaM and RyRp. Upon association with RyRp, fluorescence changes in PyN-CaM or PyC-CaM permit the measurement of the calcium-activation of these individual domains. Fluorescence changes upon calcium-activation of PyC-CaM in association with RyRp are indicative of high-affinity calcium-dependent activation of the C-terminal domain of CaM bound to RyRp at resting calcium levels and the activation of the N-terminal domain at levels of calcium associated cellular activation. In comparison, occupancy of calcium-binding sites in the N-domain of CaM mirrors the calcium-dependence of RyR1 inhibition observed at activating calcium levels, where [Ca]1/2 = 4.3 0.4 μM, suggesting a direct regulation of Ry

  6. Radioligand assay of cardiac calcium release channel and its application in SHR

    International Nuclear Information System (INIS)

    Purpose: To establish the best condition in assaying the calcium release channel (ryanodine receptor) in cardiac sarcoplasmic reticulum (CSR), and analyse the CSR ryanodine receptor in spantanous hypertensive rat (SHR). Methods: 3H-ryanodine was used as a radioligand to analyse the binding in Sprague Dawley rat cardiac homogenate in following conditions: varied protein concentrations, different free calcium concentrations, different incubation time. The effect of sarcoplasmic reticulum purifying process and ryanodine competitive binding were also studied. Using these best conditions, SHR and control group (WKY) CSR ryanodine receptor were studied. Results: 1) There was a positive linear correlation between 3H-ryanodine binding and the homogenate protein concentration. 2) When the free calcium concentration was 30 μmol/L∼1 mmol/L, the 3H-ryanodine binding reached the maximum. While the free calcium concentration was lower than 1 μmol/L, there was no 3H-ryanodine binding. 3) The 3H-ryanodine binding kept increasing during incubation, from 0 to 60 min, and equilibrium reached by 90 min. 4) The ryanodine specifically inhibited 3H-ryanodine binding in cardiac homogenate. 5) During the sarcoplasmic reticulum purifying process, the 3H-ryanodine binding in a unit amount of cardiac homogenate decreased with the centrifugal force and times applied in centrifugation. 6) SHR and WKY CSR ryanodine receptor saturation curve and Scatchard analysis showed this method produced a very high level of specific binding, up to 45 nmol/L ryanodine, which inferred a single class of binding sites. The Bmax value of CSR ryanodine receptor in SHR left ventricle was significantly higher than that in WKY (P3H-ryanodine can be used as a radioligand to analyse the calcium release channel in cardiac homogenate, and ryanodine receptor may play an important role in hypertensive left ventricular remodeling process

  7. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J;

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are...... potassium releases CGRP, and the release is regulated by Ca2+ ions and voltage-gated calcium channels....... potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ω-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  8. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J;

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are...... potassium releases CGRP, and the release is regulated by Ca2+ ions and voltage-gated calcium channels....... potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ¿-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  9. Comparison of the calcium release channel of cardiac and skeletal muscle sarcoplasmic reticulum by target inactivation analysis

    International Nuclear Information System (INIS)

    The calcium release channel of sarcoplasmic reticulum which triggers muscle contraction in excitation-contraction coupling has recently been isolated. The channel has been found to be morphologically identical with the feet structures of the junctional face membrane of terminal cisternae and consists of an oligomer of a unique high molecular weight polypeptide. In this study, the authors compare the target size of the calcium release channel from heart and skeletal muscle using target inactivation analysis. The target molecular weights of the calcium release channel estimated by measuring ryanodine binding after irradiation are similar for heart (139,000) and skeletal muscle (143,000) and are smaller than the monomeric unit (estimated to be about 360,000). The target size, estimated by measuring polypeptide remaining after irradiation, was essentially the same for heart and skeletal muscle, 1,061,000 and 1,070,000, respectively, indicating an oligomeric association of protomers. Thus, the calcium release channel of both cardiac and skeletal muscle reacts uniquely with regard to target inactivation analysis in that (1) the size by ryanodine binding is smaller than the monomeric unit and (2) a single hit leads to destruction of more than one polypeptide, by measuring polypeptide remaining. The target inactivation analysis studies indicate that heart and skeletal muscle receptors are structurally very similar

  10. Effects of inorganic mercury (Hg{sup 2+}) on calcium channel currents and catecholamine release from bovine chromaffin cells

    Energy Technology Data Exchange (ETDEWEB)

    Weinsberg, F. [Medical Inst. of Environmental Hygiene, Heinrich Heine University, Duesseldorf (Germany); Bickmeyer, U. [Medical Inst. of Environmental Hygiene, Heinrich Heine University, Duesseldorf (Germany); Wiegand, H. [Medical Inst. of Environmental Hygiene, Heinrich Heine University, Duesseldorf (Germany)

    1995-01-01

    The effects of Hg{sup 2+} on calcium channel currents and the potassium-evoked catecholamine release of bovine chromaffin cells in culture were examined. The effects of Cd{sup 2+} were studied for comparison. Calcium channel currents were recorded in the whole-cell configuration of the patch-clamp technique. In a concentration of 100 {mu}M, Hg{sup 2+} blocked the currents completely; 100 {mu}M Cd{sup 2+} had the same effect. Potassium-evoked catecholamine release from chromaffin cells was measured at different timepoints with HPLC under control conditions and in the presence of different Hg{sup 2+} concentrations. Low Hg{sup 2+} concentrations (0.1 and 1 {mu}M) did not affect the amount of the catecholamines epinephrine (E) and norepinephrine (NE) which was released. Under identical conditions 1 {mu}M Cd{sup 2+} also had no effect on release. With 10 {mu}M Hg{sup 2+} there was a time-dependent increase in the potassium-evoked catecholamine release (by 27% after 8 min). The E/NE ratio was not altered. In contrast to this, the release was slightly reduced with 10 {mu}M Cd{sup 2+}. In the presence of 100 {mu}M Hg{sup 2+}, there was a reduction of the release during an early phase, followed by an increase. The calcium channel block by 100 {mu}M Cd{sup 2+} also reduced the release significantly. Catecholamine release of bovine chromaffin cells is driven into two opposite directions by Hg{sup 2+}. On the one hand, a calcium channel block reduces the release, while on the other hand effects occur which can increase the release. Both tendencies occur simultaneously, but have different concentration- and time-dependencies. The catecholamine output at a given timepoint reflects the `sum` of these different effects. (orig.)

  11. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium channel blockers are a type of medicine used ...

  12. Contractile function is unaltered in diaphragm from mice lacking calcium release channel isoform 3

    Science.gov (United States)

    Clancy, J. S.; Takeshima, H.; Hamilton, S. L.; Reid, M. B.

    1999-01-01

    Skeletal muscle expresses at least two isoforms of the calcium release channel in the sarcoplasmic reticulum (RyR1 and RyR3). Whereas the function of RyR1 is well defined, the physiological significance of RyR3 is unclear. Some authors have suggested that RyR3 participates in excitation-contraction coupling and that RyR3 may specifically confer resistance to fatigue. To test this hypothesis, we measured contractile function of diaphragm strips from adult RyR3-deficient mice (exon 2-targeted mutation) and their heterozygous and wild-type littermates. In unfatigued diaphragm, there were no differences in isometric contractile properties (twitch characteristics, force-frequency relationships, maximal force) among the three groups. Our fatigue protocol (30 Hz, 0.25 duty cycle, 37 degrees C) depressed force to 25% of the initial force; however, lack of RyR3 did not accelerate the decline in force production. The force-frequency relationship was shifted to higher frequencies and was depressed in fatigued diaphragm; lack of RyR3 did not exaggerate these changes. We therefore provide evidence that RyR3 deficiency does not alter contractile function of adult muscle before, during, or after fatigue.

  13. Effects of Arecoline on Calcium Channel Currents and Caffeine-induced Calcium Release in Isolated Single Ventricular Myocyte of Guinea Pig

    Institute of Scientific and Technical Information of China (English)

    林先明; 李真; 胡本容; 夏国瑾; 姚伟星; 向继洲

    2002-01-01

    Summary: The effects of Arecoline (Are) on calcium mobilization were investigated. In isolatedsingle ventricular myocyte of guinea pig, patch clamp whole cell recording techniques were used torecord the current of L-type calcium channel and cytosolic Ca2+ level ([Ca2+]i) labeled with fluo-rescence probe Fluo-3/AM was measured under a laser scanning confocal microscope. Results re-vealed that Are (3-100 μmol/L) could inhibit L-type calcium current in a concentration-depen-dent manner and the value of IC50 was 33. 73μmol/L (n= 5). In the absence of extracellular calci-um, the resting levels of [Ca2+]i was not affected by Are (n=6, P>0. 05), but pretreatmentwith Are (30 μmol/L) could significantly inhibit the [Ca2+]i elevation induced by caffeine (10mmol/L, n = 6, P < 0. 01). It was concluded that Are could inhibit not only calcium influxthrough L-type calcium channel but also calcium release from sarcoplasmic reticulum.

  14. Block by ruthenium red of the ryanodine-activated calcium release channel of skeletal muscle

    OpenAIRE

    1993-01-01

    The effects of ruthenium red and the related compounds tetraamine palladium (4APd) and tetraamine platinum (4APt) were studied on the ryanodine activated Ca2+ release channel reconstituted in planar bilayers with the immunoaffinity purified ryanodine receptor. Ruthenium red, applied at submicromolar concentrations to the myoplasmic side (cis), induced an all-or-none flickery block of the ryanodine activated channel. The blocking effect was strongly voltage dependent, as large positive potenti...

  15. Calmodulin modulates the delay period between release of calcium from internal stores and activation of calcium influx via endogenous TRP1 channels.

    Science.gov (United States)

    Vaca, Luis; Sampieri, Alicia

    2002-11-01

    In the present study we have explored the role of calmodulin (CaM) and inositol 1,4,5-trisphosphate receptor (IP(3)R) in the communication process activated after the release of calcium from the endoplasmic reticulum (ER) and the activation of calcium influx via endogenous TRP1 channels from Chinese hamster ovary cells. Experiments using combined rapid confocal calcium and electrophysiology measurements uncovered a consistent delay of around 900 ms between the first detectable calcium released from the ER and the activation of the calcium current. This delay was evident with two different methods used to release calcium from the ER: either the blockade of the microsomal calcium ATPase with thapsigargin or activation of bradykinin receptors linked to the IP(3) cascade. Direct application of IP(3) or a peptide from the NH(2)-terminal region of the IP(3)R activated store operated calcium, reducing the delay period. Introduction of CaM into the cell via the patch pipette increased the delay period from 900 +/- 100 ms to 10 +/- 2.1 s (n = 18). Furthermore, the use of selective CaM antagonists W7 and trifluoperazine maleate resulted in a substantial reduction of the delay period to 200 +/- 100 ms with 5 microm trifluoperazine maleate (n = 16) and 150 +/- 50 ms with 500 nm W7 (n = 22). CaM reduced also the current density activated by thapsigargin or brandykinin to about 60% from control. The CaM antagonists did not affect significantly the current density. The results presented here are consistent with an antagonistic effect of IP(3)R and CaM for the activation of store operated calcium after depletion of the ER. The functional competition between the activating effect of IP(3)R and the inhibiting effect of CaM may modulate the delay period between the release of calcium from the ER and the activation of calcium influx observed in different cells, as well as the amount of current activated after depletion of the ER.

  16. Calcium ion channel and epilepsy

    Institute of Scientific and Technical Information of China (English)

    Yudan Lü; Weihong Lin; Dihui Ma

    2006-01-01

    OBJECTIVE: To review the relationship between calcium ion channel and epilepsy for well investigating the pathogenesis of epilepsy and probing into the new therapeutic pathway of epilepsy.DATA SOURCES: A computer-based online research Calcium ion channel and epilepsy related articles published between January 1994 and December 2006 in the CKNI and Wanfang database with the key words of "calcium influxion, epilepsy, calcium-channel blocker". The language was limited to Chinese. At the same time,related articles published between January 1993 and December 2006 in Pubmed were searched for on online with the key words of "calcium influxion, epilepsy" in English.STUDY SELECTION: The materials were selected firstly. Inclusive criteria: ① Studies related to calcium ion channel and the pat1hogenesis of epilepsy. ② Studies on the application of calcium ion channel blocker in the treatment of epilepsy. Exclusive criteria: repetitive or irrelated studies.DATA EXTRACTION: According to the criteria, 123 articles were retrieved and 93 were excluded due to repetitive or irrelated studies. Altogether 30 articles met the inclusive criteria, 11 of them were about the structure and characters of calcium ion channel, 10 about calcium ion channel and the pathogenesis of epilepsy and 9 about calcium blocker and the treatment of epilepsy.DATA SYNTHESIS: Calcium ion channels mainly consist of voltage dependent calcium channel and receptor operated calcium channel. Depolarization caused by voltage gating channel-induced influxion is the pathological basis of epileptic attack, and it is found in many studies that many anti-epileptic drugs have potential and direct effect to rivalizing voltage-dependent calcium ion channel.CONCLUSION: Calcium influxion plays an important role in the seizure of epilepsy. Some calcium antagonists seen commonly are being tried in the clinical therapy of epilepsy that is being explored, not applied in clinical practice. If there are enough evidences to

  17. Discrete stochastic modeling of calcium channel dynamics

    CERN Document Server

    Baer, M E; Levine, H; Tsimring, L S; Baer, Markus; Falcke, Martin; Levine, Herbert; Tsimring, Lev S.

    1999-01-01

    We propose a simple discrete stochastic model for calcium dynamics in living cells. Specifically, the calcium concentration distribution is assumed to give rise to a set of probabilities for the opening/closing of channels which release calcium thereby changing those probabilities. We study this model in one dimension, analytically in the mean-field limit of large number of channels per site N, and numerically for small N. As the number of channels per site is increased, the transition from a non-propagating region of activity to a propagating one changes in nature from one described by directed percolation to that of deterministic depinning in a spatially discrete system. Also, for a small number of channels a propagating calcium wave can leave behind a novel fluctuation-driven state, in a parameter range where the limiting deterministic model exhibits only single pulse propagation.

  18. Dual pathways of calcium entry in spike and plateau phases of luteinizing hormone release from chicken pituitary cells: sequential activation of receptor-operated and voltage-sensitive calcium channels by gonadotropin-releasing hormone

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, J.S.; Wakefield, I.K.; King, J.A.; Mulligan, G.P.; Millar, R.P.

    1988-04-01

    It has previously been shown that, in pituitary gonadotrope cells, the initial rise in cytosolic Ca2+ induced by GnRH is due to a Ca2+ mobilization from intracellular stores. This raises the possibility that the initial transient spike phase of LH release might be fully or partially independent of extracellular Ca2+. We have therefore characterized the extracellular Ca2+ requirements, and the sensitivity to Ca2+ channel blockers, of the spike and plateau phases of secretion separately. In the absence of extracellular Ca2+ the spike and plateau phases were inhibited by 65 +/- 4% and 106 +/- 3%, respectively. Both phases exhibited a similar dependence on concentration of extracellular Ca2+. However, voltage-sensitive Ca2+ channel blockers D600 and nifedipine had a negligible effect on the spike phase, while inhibiting the plateau phase by approximately 50%. In contrast, ruthenium red, Gd3+ ions, and Co2+ ions inhibited both spike and plateau phases to a similar extent as removal of extracellular Ca2+. A fraction (35 +/- 4%) of spike phase release was resistant to removal of extracellular Ca2+. This fraction was abolished after calcium depletion of the cells by preincubation with EGTA in the presence of calcium ionophore A23187, indicating that it depends on intracellular Ca2+ stores. Neither absence of extracellular Ca2+, nor the presence of ruthenium red or Gd3+ prevented mobilization of 45Ca2+ from intracellular stores by GnRH. We conclude that mobilization of intracellular stored Ca2+ is insufficient by itself to account for full spike phase LH release.

  19. Rapid kinetic analysis of the calcium-release channels of skeletal muscle sarcoplasmic reticulum: The effect of inhibitors

    International Nuclear Information System (INIS)

    During excitation of skeletal muscle fibers, Ca ions stored in the cisternal compartments of the sarcoplasmic reticulum (SR) are released to the cytosol within milliseconds. In this study, the kinetics of the fast release of Ca were analyzed by means of a newly developed rapid filtration apparatus. Isolated SR vesicles of cisternal origin were preloaded with 1 mM 45CaCl2, Ca efflux was studied after dilution into media of various composition. The effect of extravesicular Ca on the gating of the Ca-release channels and its susceptibility to the influence of drugs were thoroughly investigated. In the presence of 1 mM MgCl2 and 3 mM ATP, highest rates of Ca release were observed at a free Ca concentration between 1 and 50 μM. In the lower micromolar Ca range, compounds such as neomycin and FLA 365 inhibited the release monophasically and with an IC50 of 0.37 and 3.4 μM, respectively. At Ca concentrations between 10 and 50 μM, the inhibitors could not block Ca release effectively. Close analysis of the dose-response curves revealed a biphasic pattern, indicative of the presence of two substrates of the Ca-release channel, displaying high- and low-affinity binding sites for the inhibitors. The results indicate the existence of various open substrates of the Ca channels that can be distinguished pharmacologically. Effective blockade of rapid Ca release requires inhibition of all substrates coexisting under a given condition

  20. Critical role of intracellular RyR1 calcium release channels in skeletal muscle function and disease

    Directory of Open Access Journals (Sweden)

    Erick Omar Hernández-Ochoa

    2016-01-01

    Full Text Available The skeletal muscle Ca2+ release channel, also known as ryanodine receptor type 1 (RyR1, is the largest ion channel protein known and is crucial for effective skeletal muscle contractile activation. RyR1 function is controlled by Cav1.1, a voltage gated Ca2+ channel that works mainly as a voltage sensor for RyR1 activity during skeletal muscle contraction and is also fine-tuned by Ca2+, several intracellular compounds (e.g., ATP, and modulatory proteins (e.g., calmodulin. Dominant and recessive mutations in RyR1, as well as acquired channel alterations, are the underlying cause of various skeletal muscle diseases. The aim of this mini review is to summarize several current aspects of RyR1 function, structure, regulation, and to describe the most common diseases caused by hereditary or acquired RyR1 malfunction.

  1. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, Trine Meldgaard; Belhage, B;

    2001-01-01

    The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured...... using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...... most important voltage dependent calcium channel in all parts of the neuron. After treatment with thapsigargin the increase in cytosolic calcium was halved, indicating that calcium release from thapsigargin sensitive intracellular calcium stores is an important component of the potassium induced rise...

  2. Localization of large conductance calcium-activated potassium channels and their effect on calcitonin gene-related peptide release in the rat trigemino-neuronal pathway

    DEFF Research Database (Denmark)

    Wulf-Johansson, H.; Amrutkar, D.V.; Hay-Schmidt, Anders;

    2010-01-01

    Large conductance calcium-activated potassium (BK(Ca)) channels are membrane proteins contributing to electrical propagation through neurons. Calcitonin gene-related peptide (CGRP) is a neuropeptide found in the trigeminovascular system (TGVS). Both BK(Ca) channels and CGRP are involved in migraine...

  3. Construction of calcium release sites in cardiac myocytes

    Directory of Open Access Journals (Sweden)

    Alexandra eZahradnikova

    2012-08-01

    Full Text Available Local character of calcium release in cardiac myocytes, as defined by confocal recordings of calcium sparks, implies independent activation of individual calcium release sites based on ryanodine receptor (RyR channel recruitment. We constructed virtual calcium release sites (vCRSs composed of a variable number of RyR channels distributed in clusters in accordance with the experimentally observed cluster size distribution. The vCRSs consisted either of a single virtual calcium release unit, in which all clusters shared a common dyadic space, or of multiple virtual calcium release units containing one cluster each and having separate dyadic spaces. We explored the stochastic behavior of vCRSs to understand the activation and recruitment of RyRs during calcium sparks. RyRs were represented by the published allosteric gating model that included regulation by cytosolic Ca2+ and Mg2+. The interaction of Mg2+ with the RyR Ca2+-binding sites and the refractory period of vCRSs were optimized to accord with the experimentally observed calcium dependence of calcium spark frequency. The Mg2+-binding parameters of RyRs that provided the best description of spark frequency depended on the number of RyRs assembled in the virtual calcium release sites. Adequate inhibitory effect of Mg2+ on the calcium dependence of RyR open probability was achieved if the virtual calcium release sites contained at least three clusters. For the distribution of the number of open RyRs in evoked calcium sparks to correspond to the experimentally observed distribution of spark calcium release fluxes, at least 3 clusters had to share a common virtual calcium release unit, in which ~ 3 RyRs open to form an average spark. These results reconcile the small cluster size and stochastic placement of RyRs in the release sites with the estimates of the amount of RyR protein, volume density of calcium release sites, and the size of calcium release sites in rat cardiac myocytes.

  4. Calcium homeostasis modulator (CALHM) ion channels.

    Science.gov (United States)

    Ma, Zhongming; Tanis, Jessica E; Taruno, Akiyuki; Foskett, J Kevin

    2016-03-01

    Calcium homeostasis modulator 1 (CALHM1), formerly known as FAM26C, was recently identified as a physiologically important plasma membrane ion channel. CALHM1 and its Caenorhabditis elegans homolog, CLHM-1, are regulated by membrane voltage and extracellular Ca(2+) concentration ([Ca(2+)]o). In the presence of physiological [Ca(2+)]o (∼1.5 mM), CALHM1 and CLHM-1 are closed at resting membrane potentials but can be opened by strong depolarizations. Reducing [Ca(2+)]o increases channel open probability, enabling channel activation at negative membrane potentials. Together, voltage and Ca(2+) o allosterically regulate CALHM channel gating. Through convergent evolution, CALHM has structural features that are reminiscent of connexins and pannexins/innexins/LRRC8 (volume-regulated anion channel (VRAC)) gene families, including four transmembrane helices with cytoplasmic amino and carboxyl termini. A CALHM1 channel is a hexamer of CALHM1 monomers with a functional pore diameter of ∼14 Å. CALHM channels discriminate poorly among cations and anions, with signaling molecules including Ca(2+) and ATP able to permeate through its pore. CALHM1 is expressed in the brain where it plays an important role in cortical neuron excitability induced by low [Ca(2+)]o and in type II taste bud cells in the tongue that sense sweet, bitter, and umami tastes where it functions as an essential ATP release channel to mediate nonsynaptic neurotransmitter release. CLHM-1 is expressed in C. elegans sensory neurons and body wall muscles, and its genetic deletion causes locomotion defects. Thus, CALHM is a voltage- and Ca(2+) o-gated ion channel, permeable to large cations and anions, that plays important roles in physiology. PMID:26603282

  5. Calcium channel blockers and Alzheimer's disease

    Institute of Scientific and Technical Information of China (English)

    Yi Tan; Yulin Deng; Hong Qing

    2012-01-01

    Alzheimer's disease is characterized by two pathological hallmarks: amyloid plaques and neurofi-brillary tangles. In addition, calcium homeostasis is disrupted in the course of human aging. Recent research shows that dense plaques can cause functional alteration of calcium signals in mice with Alzheimer's disease. Calcium channel blockers are effective therapeutics for treating Alzheimer's disease. This review provides an overview of the current research of calcium channel blockers in-volved in Alzheimer's disease therapy.

  6. Growth differentiation factor-15 promotes glutamate release in medial prefrontal cortex of mice through upregulation of T-type calcium channels

    Science.gov (United States)

    Liu, Dong-Dong; Lu, Jun-Mei; Zhao, Qian-Ru; Hu, Changlong; Mei, Yan-Ai

    2016-01-01

    Growth differentiation factor-15 (GDF-15) has been implicated in ischemic brain injury and synapse development, but its involvement in modulating neuronal excitability and synaptic transmission remain poorly understood. In this study, we investigated the effects of GDF-15 on non-evoked miniature excitatory post-synaptic currents (mEPSCs) and neurotransmitter release in the medial prefrontal cortex (mPFC) in mice. Incubation of mPFC slices with GDF-15 for 60 min significantly increased the frequency of mEPSCs without effect on their amplitude. GDF-15 also significantly elevated presynaptic glutamate release, as shown by HPLC. These effects were blocked by dual TGF-β type I receptor (TβRI) and TGF-β type II receptor (TβRII) antagonists, but not by a TβRI antagonist alone. Meanwhile, GDF-15 enhanced pERK level, and inhibition of MAPK/ERK activity attenuated the GDF-15-induced increases in mEPSC and glutamate release. Blocking T-type calcium channels reduced the GDF-15 induced up-regulation of synaptic transmission. Membrane-protein extraction and use of an intracellular protein-transport inhibitor showed that GDF-15 promoted CaV3.1 and CaV3.3 α-subunit expression by trafficking to the membrane. These results confirm previous findings in cerebellar granule neurons, in which GDF-15 induces its neurobiological effects via TβRII and activation of the ERK pathway, providing novel insights into the mechanism of GDF-15 function in cortical neurons. PMID:27353765

  7. Osteoblasts detect pericellular calcium concentration increase via neomycin-sensitive voltage gated calcium channels.

    Science.gov (United States)

    Sun, Xuanhao; Kishore, Vipuil; Fites, Kateri; Akkus, Ozan

    2012-11-01

    The mechanisms underlying the detection of critically loaded or micro-damaged regions of bone by bone cells are still a matter of debate. Our previous studies showed that calcium efflux originates from pre-failure regions of bone matrix and MC3T3-E1 osteoblasts respond to such efflux by an increase in the intracellular calcium concentration. The mechanisms by which the intracellular calcium concentration increases in response to an increase in the pericellular calcium concentration are unknown. Elevation of the intracellular calcium may occur via release from the internal calcium stores of the cell and/or via the membrane bound channels. The current study applied a wide range of pharmaceutical inhibitors to identify the calcium entry pathways involved in the process: internal calcium release from endoplasmic reticulum (ER, inhibited by thapsigargin and TMB-8), calcium receptor (CaSR, inhibited by calhex), stretch-activated calcium channel (SACC, inhibited by gadolinium), voltage-gated calcium channels (VGCC, inhibited by nifedipine, verapamil, neomycin, and ω-conotoxin), and calcium-induced-calcium-release channel (CICRC, inhibited by ryanodine and dantrolene). These inhibitors were screened for their effectiveness to block intracellular calcium increase by using a concentration gradient induced calcium efflux model which mimics calcium diffusion from the basal aspect of cells. The inhibitor(s) which reduced the intracellular calcium response was further tested on osteoblasts seeded on mechanically loaded notched cortical bone wafers undergoing damage. The results showed that only neomycin reduced the intracellular calcium response in osteoblasts, by 27%, upon extracellular calcium stimulus induced by concentration gradient. The inhibitory effect of neomycin was more pronounced (75% reduction in maximum fluorescence) for osteoblasts seeded on notched cortical bone wafers loaded mechanically to damaging load levels. These results imply that the increase in

  8. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, T M; Belhage, B;

    2001-01-01

    in cytosolic calcium concentration. The results of this investigation demonstrate that pharmacologically distinct types of voltage dependent calcium channels are differentially localized in cell bodies, neurites and nerve terminals of mouse cortical neurons but that the Q-type calcium channel appears......The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured...... using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...

  9. Extent of use of immediate-release formulations of calcium channel blockers as antihypertensive monotherapy by primary care physicians: multicentric study from Bahrain.

    Directory of Open Access Journals (Sweden)

    Sequeira R

    2002-07-01

    Full Text Available BACKGROUND: The issue of cardiovascular safety of calcium channel blockers (CCBs has been widely debated in view of reflex increase in sympathetic activity induced by immediate release (IR / short acting formulations. It is generally agreed that such CCBs should not be used alone in the management of hypertension. AIMS: We have determined the extent to which primary care physicians prescribe CCBs as monotherapy, especially the immediate release formulations, in the management of uncomplicated hypertension and diabetic hypertension - with an emphasis upon the age of the patients. SETTING, DESIGN AND METHODS: A retrospective prescription-based study was carried out in seven out of 18 Health Centres in Bahrain. The study involved a registered population of 229,300 representing 46% of registered individuals, and 35 physicians representing 43% of all primary care physicians. The data was collected between November 1998 and January 1999 using chronic dispensing cards. RESULTS: In all categories CCBs were the third commonly prescribed antihypertensive as monotherapy, with a prescription rate of 11.1% in uncomplicated hypertension, 18% in diabetic hypertension and 20.1% in elderly patients above 65 years of age. Nifedipine formulations were the most extensively prescribed CCBs. Almost half of the CCB-treated patients were on IR-nifedipine, whereas IR-diltiazem and IR-verapamil, and amlodipine were infrequently prescribed. CONCLUSION: Prescription of IR-formulations of CCBs as monotherapy by primary care physicians does not conform with recommended guidelines. In view of concerns about the safety of such practice, measures to change the prescribing pattern are required.

  10. Calcium channel as a potential anticancer agent.

    Science.gov (United States)

    Kriazhev, L

    2009-11-01

    Anticancer treatment in modern clinical practices includes chemotherapy and radiation therapy with or without surgical interventions. Efficiency of both methods varies greatly depending on cancer types and stages. Besides, chemo- and radiotherapy are toxic and damaging that causes serious side effects. This fact prompts the search for alternative methods of antitumor therapy. It is well known that prolonged or high increase of intracellular calcium concentration inevitably leads to the cell death via apoptosis or necrosis. However, stimulation of cell calcium level by chemical agents is hardly achievable because cells have very sophisticated machinery for maintaining intracellular calcium in physiological ranges. This obstacle can be overridden, nevertheless. It was found that calcium channels in so called calcium cells in land snails are directly regulated by extracellular calcium concentration. The higher the concentration the higher the calcium intake is through the channels. Bearing in mind that extracellular/intracellular calcium concentration ratio in human beings is 10,000-12,000 fold the insertion of the channel into cancer cells would lead to fast and uncontrollable by the cells calcium intake and cell death. Proteins composing the channel may be extracted from plasma membrane of calcium cells and sequenced by mass-spectrometry or N-terminal sequencing. Either proteins or corresponding genes could be used for targeted delivery into cancer cells.

  11. Discrete Stochastic Modeling of Calcium Channel Dynamics

    International Nuclear Information System (INIS)

    We propose a discrete stochastic model for calcium dynamics in living cells. A set of probabilities for the opening/closing of calcium channels is assumed to depend on the calcium concentration. We study this model in one dimension, analytically in the limit of a large number of channels per site N , and numerically for small N . As the number of channels per site is increased, the transition from a nonpropagating region of activity to a propagating one changes from one described by directed percolation to that of deterministic depinning in a spatially discrete system. Also, for a small number of channels a propagating calcium wave can leave behind a novel fluctuation-driven state. (c) 2000 The American Physical Society

  12. Mobility of calcium channels in the presynaptic membrane.

    Science.gov (United States)

    Schneider, Romy; Hosy, Eric; Kohl, Johannes; Klueva, Julia; Choquet, Daniel; Thomas, Ulrich; Voigt, Andreas; Heine, Martin

    2015-05-01

    Unravelling principles underlying neurotransmitter release are key to understand neural signaling. Here, we describe how surface mobility of voltage-dependent calcium channels (VDCCs) modulates release probabilities (P(r)) of synaptic vesicles (SVs). Coupling distances of 100 nm have been reported for SVs and VDCCs in different synapses. Tracking individual VDCCs revealed that within hippocampal synapses, ∼60% of VDCCs are mobile while confined to presynaptic membrane compartments. Intracellular Ca(2+) chelation decreased VDCC mobility. Increasing VDCC surface populations by co-expression of the α2δ1 subunit did not alter channel mobility but led to enlarged active zones (AZs) rather than higher channel densities. VDCCs thus scale presynaptic scaffolds to maintain local mobility. We propose that dynamic coupling based on mobile VDCCs supports calcium domain cooperativity and tunes neurotransmitter release by equalizing Pr for docked SVs within AZs. PMID:25892305

  13. Expanding the neuron's calcium signaling repertoire: intracellular calcium release via voltage-induced PLC and IP3R activation.

    Directory of Open Access Journals (Sweden)

    Stefanie Ryglewski

    2007-04-01

    Full Text Available Neuronal calcium acts as a charge carrier during information processing and as a ubiquitous intracellular messenger. Calcium signals are fundamental to numerous aspects of neuronal development and plasticity. Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert. This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons. These neurons possess a membrane voltage sensor that, independent of calcium influx, causes G-protein activation, which subsequently leads to calcium release from intracellular stores via phospholipase C and inositol 1,4,5-trisphosphate receptor activation. This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

  14. Calcium binding protein-mediated regulation of voltage-gated calcium channels linked to human diseases

    Institute of Scientific and Technical Information of China (English)

    Nasrin NFJATBAKHSH; Zhong-ping FENG

    2011-01-01

    Calcium ion entry through voltage-gated calcium channels is essential for cellular signalling in a wide variety of cells and multiple physiological processes. Perturbations of voltage-gated calcium channel function can lead to pathophysiological consequences. Calcium binding proteins serve as calcium sensors and regulate the calcium channel properties via feedback mechanisms. This review highlights the current evidences of calcium binding protein-mediated channel regulation in human diseases.

  15. Characterization of dihydropyridine-sensitive calcium channels

    International Nuclear Information System (INIS)

    The structural and regulatory properties of the dihydropyridine-sensitive calcium channel were studied by isolating protein components of the channel complex from both cardiac and skeletal muscle. Hydrodynamic characterization of the (+)-(3H)PN200-110-labeled cardiac calcium channel revealed that the protein components of the complex had a total molecular mass of 370,000 daltons, a Stokes radius of 86 angstrom, and a frictional ratio of 1.3. A technique is described for the rapid incorporation of the CHAPS solubilized skeletal muscle calcium channel complex into phospholipid vesicles. 45Ca2+ uptake into phospholipid vesicles containing calcium channels was inhibited by phenylalkalamine calcium antagonists. Wheat germ lectin followed by DEAE chromatography of the CHAPS solubilized complex resulted in the dissociation of regulatory components of the complex from channel components. The DEAE preparation gave rise to 45Ca2+ uptake that was not inhibited by verapamil but was inhibited by GTPgS activated G0. The inhibition of 45Ca2+ uptake by verapamil was restored by co-reconstitution of wash fractions from wheat germ lectin chromatography. Phosphorylation of polypeptides in this fraction by polypeptide-dependent protein kinase prevented the restoration of verapamil sensitivity. The partial purification of an endogenous skeletal muscle ADP-ribosyltransferase is also described. ADP-ribosylation of the α2 subunit of the calcium channel complex is enhanced by polylysine and inhibited by GTPγS, suggesting that regulation of this enzyme is under the control of GTP binding proteins. These results suggest a complex model, involving a number of different protein components, for calcium channel regulation in skeletal muscle

  16. Calcium signals and calcium channels in osteoblastic cells

    Science.gov (United States)

    Duncan, R. L.; Akanbi, K. A.; Farach-Carson, M. C.

    1998-01-01

    Calcium (Ca2+) channels are present in non-excitable as well as in excitable cells. In bone cells of the osteoblast lineage, Ca2+ channels play fundamental roles in cellular responses to external stimuli including both mechanical forces and hormonal signals. They are also proposed to modulate paracrine signaling between bone-forming osteoblasts and bone-resorbing osteoclasts at local sites of bone remodeling. Calcium signals are characterized by transient increases in intracellular Ca2+ levels that are associated with activation of intracellular signaling pathways that control cell behavior and phenotype, including patterns of gene expression. Development of Ca2+ signals is a tightly regulated cellular process that involves the concerted actions of plasma membrane and intracellular Ca2+ channels, along with Ca2+ pumps and exchangers. This review summarizes the current state of knowledge concerning the structure, function, and role of Ca2+ channels and Ca2+ signals in bone cells, focusing on the osteoblast.

  17. Dihydropyridine-sensitive calcium channel activity related to prolactin, growth hormone, and luteinizing hormone release from anterior pituitary cells in culture: interactions with somatostatin, dopamine, and estrogens

    International Nuclear Information System (INIS)

    In the present work, we determined the activity of voltage-dependent dihydropyridine (DHP)-sensitive Ca2+ channels related to PRL, GH, and LH secretion in primary cultures of pituitary cells from male or female rats. We investigated their modulation by 17 beta-estradiol (E2) and their involvement in dopamine (DA) and somatostatin (SRIF) inhibition of PRL and GH release. BAY-K-8644 (BAYK), a DHP agonist which increases the opening time of already activated channels, stimulated PRL and GH secretion in a dose-dependent manner. The effect was more pronounced on PRL than on GH release. BAYK-evoked hormone secretion was further amplified by simultaneous application of K+ (30 or 56 mM) to the cell cultures; in parallel, BAYK-induced 45Ca uptake by the cells was potentiated in the presence of depolarizing stimuli. In contrast, BAYK was unable to stimulate LH secretion from male pituitary cells, but it potentiated LHRH- as well as K+-induced LH release; it had only a weak effect on LH secretion from female cell cultures. Basal and BAYK-induced pituitary hormone release were blocked by the Ca2+ channel antagonist nitrendipine. Under no condition did BAYK affect the hydrolysis of phosphoinositides or cAMP formation. Pretreatment of female pituitary cell cultures with E2 (10(-9) M) for 72 h enhanced LH and PRL responses to BAYK, but was ineffective on GH secretion. DA (10(-7) M) inhibited basal and BAYK-induced PRL release from male or female pituitary cells treated or not treated with E2 (10(-9) M). SRIF (10(-9) and 10(-8) M) reversed BAYK-evoked GH release to the same extent in cell cultures derived from male or female animals. It was ineffective on BAYK-induced PRL secretion in the absence of E2, but antagonized it after E2 pretreatment. The effect was dependent upon the time of steroid treatment and was specific, since 17 alpha-estradiol was inactive

  18. Markov chain models of coupled calcium channels: Kronecker representations and iterative solution methods

    International Nuclear Information System (INIS)

    Mathematical models of calcium release sites derived from Markov chain models of intracellular calcium channels exhibit collective gating reminiscent of the experimentally observed phenomenon of stochastic calcium excitability (i.e., calcium puffs and sparks). Calcium release site models are stochastic automata networks that involve many functional transitions, that is, the transition probabilities of each channel depend on the local calcium concentration and thus the state of the other channels. We present a Kronecker-structured representation for calcium release site models and perform benchmark stationary distribution calculations using both exact and approximate iterative numerical solution techniques that leverage this structure. When it is possible to obtain an exact solution, response measures such as the number of channels in a particular state converge more quickly using the iterative numerical methods than occupation measures calculated via Monte Carlo simulation. In particular, multi-level methods provide excellent convergence with modest additional memory requirements for the Kronecker representation of calcium release site models. When an exact solution is not feasible, iterative approximate methods based on the power method may be used, with performance similar to Monte Carlo estimates. This suggests approximate methods with multi-level iterative engines as a promising avenue of future research for large-scale calcium release site models

  19. Calcium channel-dependent molecular maturation of photoreceptor synapses.

    Directory of Open Access Journals (Sweden)

    Nawal Zabouri

    Full Text Available Several studies have shown the importance of calcium channels in the development and/or maturation of synapses. The Ca(V1.4(α(1F knockout mouse is a unique model to study the role of calcium channels in photoreceptor synapse formation. It features abnormal ribbon synapses and aberrant cone morphology. We investigated the expression and targeting of several key elements of ribbon synapses and analyzed the cone morphology in the Ca(V1.4(α(1F knockout retina. Our data demonstrate that most abnormalities occur after eye opening. Indeed, scaffolding proteins such as Bassoon and RIM2 are properly targeted at first, but their expression and localization are not maintained in adulthood. This indicates that either calcium or the Ca(V1.4 channel, or both are necessary for the maintenance of their normal expression and distribution in photoreceptors. Other proteins, such as Veli3 and PSD-95, also display abnormal expression in rods prior to eye opening. Conversely, vesicle related proteins appear normal. Our data demonstrate that the Ca(V1.4 channel is important for maintaining scaffolding proteins in the ribbon synapse but less vital for proteins related to vesicular release. This study also confirms that in adult retinae, cones show developmental features such as sprouting and synaptogenesis. Overall we present evidence that in the absence of the Ca(V1.4 channel, photoreceptor synapses remain immature and are unable to stabilize.

  20. Cardiac calcium release channel (ryanodine receptor) in control and cardiomyopathic human hearts: mRNA and protein contents are differentially regulated.

    Science.gov (United States)

    Sainte Beuve, C; Allen, P D; Dambrin, G; Rannou, F; Marty, I; Trouvé, P; Bors, V; Pavie, A; Gandgjbakch, I; Charlemagne, D

    1997-04-01

    Abnormal intracellular calcium handling in cardiomyopathic human hearts has been associated with an impaired function of the sarcoplasmic reticulum, but previous reports on the gene expression of the ryanodine receptors (Ry2) are contradictory. We measured the mRNA levels, the protein levels and the number of high affinity [3H]ryanodine binding sites in the left ventricle of non-failing (n = 9) and failing human hearts [idiopathic dilated (IDCM n = 16), ischemic (ICM n = 7) or mixed (MCM n = 8) cardiomyopathies]. Ry2 mRNA levels were significantly reduced in IDCM (-30%) and unchanged in MCM and ICM and Ry2 protein levels were similar. In contrast, we observed a two-fold increase in the number of high affinity Ry2 (B(max) = 0.43 +/- 0.11 v 0.22 +/- 0.13 pmol/mg protein, respectively; P<0.01) and an unchanged K(d). Furthermore, levels of myosin heavy chain mRNA and protein per g of tissue were similar in failing and non-failing hearts, suggesting that the observed differences in Ry2 are not caused by the increase in fibrosis in failing heart. Therefore, the dissociation between the two-fold increase in the number of high affinity ryanodine receptors observed in all failing hearts and the slightly decreased mRNA level or unchanged protein level suggests that the ryanodine binding properties are affected in failing myocardium and that such modifications rather than a change in gene expression alter the channel activity and could contribute to abnormalities in intracellular Ca2+ handling. PMID:9160875

  1. Binding of [125I]iodipine to parathyroid cell membranes: Evidence of a dihydropyridine-sensitive calcium channel

    International Nuclear Information System (INIS)

    The parathyroid cell is unusual, in that an increase in extracellular calcium concentrations inhibits PTH release. Calcium channels are glycoproteins that span cell membranes and allow entry of extracellular calcium into cells. We have demonstrated that the calcium channel agonist (+)202-791, which opens calcium channels, inhibits PTH release and that the antagonist (-)202-791, which closes calcium channels, stimulates PTH release. To identify the calcium channels responsible for these effects, we used a radioligand that specifically binds to calcium channels. Bovine parathyroid cell membranes were prepared and incubated under reduced lighting with [125I] iodipine (SA, 2000 Ci/mmol), which recognizes 1,4-dihydropyridine-sensitive calcium channels. Bound ligand was separated from free ligand by rapid filtration through Whatman GF/B filters. Nonspecific binding was measured by the inclusion of nifedipine at 10 microM. Specific binding represented approximately 40% of the total binding. The optimal temperature for [125I] iodipine binding was 4 C, and binding reached equilibrium by 30 min. The equilibrium dissociation constant (Kd) was approximately 550 pM, and the maximum number of binding sites was 780 fmol/mg protein. Both the calcium channel agonist (+)202-791 and antagonist (-)202-791 competitively inhibited [125I] iodipine binding, with 50% inhibition concentrations of 20 and 300 nM, respectively. These data indicate the presence of dihydropyridine-sensitive calcium channels on parathyroid cell membranes

  2. Activation of a cGMP-sensitive calcium-dependent chloride channel may cause transition from calcium waves to whole cell oscillations in smooth muscle cells

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian Brings; Aalkjær, Christian; Nilsson, Holger;

    2007-01-01

    waves sweeping through the cytoplasm when the sarcoplasmic reticulum (SR) is stimulated to release calcium. A rise in cGMP leads to the experimentally observed transition from waves to whole cell calcium oscillations. At the same time, membrane potential starts to oscillate and the frequency...... approximately doubles. In this transition, the simulated results point to a key role for a recently discovered cGMP-sensitive calcium-dependent chloride channel. This channel depolarizes the membrane in response to calcium released from the SR. In turn, depolarization causes a uniform opening of L-type calcium...

  3. Opening of small and intermediate calcium-activated potassium channels induces relaxation mainly mediated by nitric-oxide release in large arteries and endothelium-derived hyperpolarizing factor in small arteries from rat

    DEFF Research Database (Denmark)

    Stankevicius, Edgaras; Dalsgaard, Thomas; Kroigaard, Christel;

    2011-01-01

    current, and NO release that were blocked by apamin and TRAM-34 or charybdotoxin. These findings suggest that opening of SK(Ca) and IK(Ca) channels leads to endothelium-dependent relaxation that is mediated mainly by NO in large mesenteric arteries and by EDHF-type relaxation in small mesenteric arteries......This study was designed to investigate whether calcium-activated potassium channels of small (SK(Ca) or K(Ca)2) and intermediate (IK(Ca) or K(Ca)3.1) conductance activated by 6,7-dichloro-1H-indole-2,3-dione 3-oxime (NS309) are involved in both nitric oxide (NO) and endothelium......-derived hyperpolarizing factor (EDHF)-type relaxation in large and small rat mesenteric arteries. Segments of rat superior and small mesenteric arteries were mounted in myographs for functional studies. NO was recorded using NO microsensors. SK(Ca) and IK(Ca) channel currents and mRNA expression were investigated in...

  4. Calcium release-activated calcium current in rat mast cells.

    Science.gov (United States)

    Hoth, M; Penner, R

    1993-06-01

    1. Whole-cell patch clamp recordings of membrane currents and fura-2 measurements of free intracellular calcium concentration ([Ca2+]i) were used to study the biophysical properties of a calcium current activated by depletion of intracellular calcium stores in rat peritoneal mast cells. 2. Calcium influx through an inward calcium release-activated calcium current (ICRAC) was induced by three independent mechanisms that result in store depletion: intracellular infusion of inositol 1,4,5-trisphosphate (InsP3) or extracellular application of ionomycin (active depletion), and intracellular infusion of calcium chelators (ethylene glycol bis-N,N,N',N'-tetraacetic acid (EGTA) or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA)) to prevent reuptake of leaked-out calcium into the stores (passive depletion). 3. The activation of ICRAC induced by active store depletion has a short delay (4-14 s) following intracellular infusion of InsP3 or extracellular application of ionomycin. It has a monoexponential time course with a time constant of 20-30 s and, depending on the complementary Ca2+ buffer, a mean normalized amplitude (at 0 mV) of 0.6 pA pF-1 (with EGTA) and 1.1 pA pF-1 (with BAPTA). 4. After full activation of ICRAC by InsP3 in the presence of EGTA (10 mM), hyperpolarizing pulses to -100 mV induced an instantaneous inward current that decayed by 64% within 50 ms. This inactivation is probably mediated by [Ca2+]i, since the decrease of inward current in the presence of the fast Ca2+ buffer BAPTA (10 mM) was only 30%. 5. The amplitude of ICRAC was dependent on the extracellular Ca2+ concentration with an apparent dissociation constant (KD) of 3.3 mM. Inward currents were nonsaturating up to -200 mV. 6. The selectivity of ICRAC for Ca2+ was assessed by using fura-2 as the dominant intracellular buffer (at a concentration of 2 mM) and relating the absolute changes in the calcium-sensitive fluorescence (390 nm excitation) with the calcium current integral

  5. Teaching Calcium-Induced Calcium Release in Cardiomyocytes Using a Classic Paper by Fabiato

    Science.gov (United States)

    Liang, Willmann

    2008-01-01

    This teaching paper utilizes the materials presented by Dr. Fabiato in his review article entitled "Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum." In the review, supporting evidence of calcium-induced calcium release (CICR) is presented. Data concerning potential objections to the CICR theory are discussed as well. In…

  6. Spontaneous Neurotransmitter Release Depends on Intracellular Rather than ER Calcium Stores in Cultured Xenopus NMJ

    Institute of Scientific and Technical Information of China (English)

    GE Song; LI Ruxin; QI Lei; HE Xiangping; XIE Zuoping

    2006-01-01

    Calcium ions are important in many vital neuron processes, including spontaneous neurotransmitter release. Extracellular calcium has long been known to be related to spontaneous neurotransmitter release, but the detailed mechanism for the effect of intracellular Ca2+ on synaptic release has not yet been understood. In this research, 1,2-bis-(o-aminophenoxy)-ethane-N, N, N', N'-tetraacetic acid tetraacetoxy-methyl ester (BAPTA-AM) was used to combine with cytosolic free Ca2+ in a calcium free medium of cultured Xenopus neuromuscular junctions (NMJ). The spontaneous synaptic current (SSC) frequency was obviously reduced. Then, drugs were applied to interrupt and activate the Ca2+ release channels in the endoplasmic reticulum (ER) membrane, but the SSC frequency was not affected. The results show that spontaneous neurotransmitter release depends on intracellular rather than ER calcium in cultured Xenopus NMJ without extracellular calcium.

  7. A calcium-induced calcium release mechanism mediated by calsequestrin.

    Science.gov (United States)

    Lee, Young-Seon; Keener, James P

    2008-08-21

    Calcium (Ca(2+))-induced Ca(2+) release (CICR) is widely accepted as the principal mechanism linking electrical excitation and mechanical contraction in cardiac cells. The CICR mechanism has been understood mainly based on binding of cytosolic Ca(2+) with ryanodine receptors (RyRs) and inducing Ca(2+) release from the sarcoplasmic reticulum (SR). However, recent experiments suggest that SR lumenal Ca(2+) may also participate in regulating RyR gating through calsequestrin (CSQ), the SR lumenal Ca(2+) buffer. We investigate how SR Ca(2+) release via RyR is regulated by Ca(2+) and calsequestrin (CSQ). First, a mathematical model of RyR kinetics is derived based on experimental evidence. We assume that the RyR has three binding sites, two cytosolic sites for Ca(2+) activation and inactivation, and one SR lumenal site for CSQ binding. The open probability (P(o)) of the RyR is found by simulation under controlled cytosolic and SR lumenal Ca(2+). Both peak and steady-state P(o) effectively increase as SR lumenal Ca(2+) increases. Second, we incorporate the RyR model into a CICR model that has both a diadic space and the junctional SR (jSR). At low jSR Ca(2+) loads, CSQs are more likely to bind with the RyR and act to inhibit jSR Ca(2+) release, while at high SR loads CSQs are more likely to detach from the RyR, thereby increasing jSR Ca(2+) release. Furthermore, this CICR model produces a nonlinear relationship between fractional jSR Ca(2+) release and jSR load. These findings agree with experimental observations in lipid bilayers and cardiac myocytes. PMID:18538346

  8. Treatment for calcium channel blocker poisoning: A systematic review

    OpenAIRE

    St-Onge, M.; Dubé, P.-A.; Gosselin, S.; Guimont, C; Godwin, J; Archambault, P. M.; Chauny, J.-M.; Frenette, A. J.; Darveau, M.; Le sage, N.; Poitras, J.; Provencher, J.; Juurlink, D. N.; Blais, R

    2014-01-01

    Context Calcium channel blocker poisoning is a common and sometimes life-threatening ingestion. Objective To evaluate the reported effects of treatments for calcium channel blocker poisoning. The primary outcomes of interest were mortality and hemodynamic parameters. The secondary outcomes included length of stay in hospital, length of stay in intensive care unit, duration of vasopressor use, functional outcomes, and serum calcium channel blocker concentrations. Methods Medline/Ovid, PubMed, ...

  9. Diffusive spatio-temporal noise in a first-passage time model for intracellular calcium release

    KAUST Repository

    Flegg, Mark B.

    2013-01-01

    The intracellular release of calcium from the endoplasmic reticulum is controlled by ion channels. The resulting calcium signals exhibit a rich spatio-temporal signature, which originates at least partly from microscopic fluctuations. While stochasticity in the gating transition of ion channels has been incorporated into many models, the distribution of calcium is usually described by deterministic reaction-diffusion equations. Here we test the validity of the latter modeling approach by using two different models to calculate the frequency of localized calcium signals (calcium puffs) from clustered IP3 receptor channels. The complexity of the full calcium system is here limited to the basic opening mechanism of the ion channels and, in the mathematical reduction simplifies to the calculation of a first passage time. Two models are then studied: (i) a hybrid model, where channel gating is treated stochastically, while calcium concentration is deterministic and (ii) a fully stochastic model with noisy channel gating and Brownian calcium ion motion. The second model utilises the recently developed two-regime method [M. B. Flegg, S. J. Chapman, and R. Erban, "The two-regime method for optimizing stochastic reaction-diffusion simulations," J. R. Soc., Interface 9, 859-868 (2012)] in order to simulate a large domain with precision required only near the Ca2+ absorbing channels. The expected time for a first channel opening that results in a calcium puff event is calculated. It is found that for a large diffusion constant, predictions of the interpuff time are significantly overestimated using the model (i) with a deterministic non-spatial calcium variable. It is thus demonstrated that the presence of diffusive noise in local concentrations of intracellular Ca2+ ions can substantially influence the occurrence of calcium signals. The presented approach and results may also be relevant for other cell-physiological first-passage time problems with small ligand concentration

  10. Physiology and Regulation of Calcium Channels in Stomatal Guard Cells

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Julian I.

    2007-05-02

    Stomatal pores in the epidermis of leaves regulate the diffusion of CO2 into leaves for photosynthetic carbon fixation and control water loss of plants during drought periods. Guard cells sense CO2, water status, light and other environmental conditions to regulate stomatal apertures for optimization of CO2 intake and plant growth under drought stress. The cytosolic second messenger calcium contributes to stomatal movements by transducing signals and regulating ion channels in guard cells. Studies suggest that both plasma membrane Ca2+ influx channels and vacuolar/organellar Ca2+ release channels contribute to ABA-induced Ca2+ elevations in guard cells. Recent research in the P.I.'s laboratory has led to identification of a novel major cation-selective Ca2+-permeable influx channel (Ica) in the plasma membrane of Arabidopsis guard cells. These advances will allow detailed characterization of Ica plasma membrane Ca2+ influx channels in guard cells. The long term goal of this research project is to gain a first detailed characterization of these novel plasma membrane Ca2+-permeable channel currents in Arabidopsis guard cells. The proposed research will investigate the hypothesis that Ica represents an important Ca2+ influx pathway for ABA and CO2 signal transduction in Arabidopsis guard cells. These studies will lead to elucidation of key signal transduction mechanisms by which plants balance CO2 influx into leaves and transpirational water loss and may contribute to future strategies for manipulating gas exchange for improved growth of crop plants and for biomass production.

  11. Magnesium: Effect on ocular health as a calcium channel antagonist

    Directory of Open Access Journals (Sweden)

    Şafak Korkmaz

    2013-06-01

    Full Text Available Magnesium is the physiologic calcium channel blocker,involving in many different metabolic processes by maintainingcell membrane function, modulating smooth musclecontraction and influencing enzymatic activities. Magnesiumhas been shown to increase blood flow to tissuesby modifying endothelial function via endothelin-1 (ET-1and nitric Oxide (NO pathways. Magnesium also exhibitsneuroprotective role by blocking N-methyl-D-aspartate(NMDA receptor related calcium influx and by inhibitingthe release of glutamate, hence protects the cell againstoxidative stress and apoptosis. Both increase in bloodflow and its neuroprotective effect make magnesium agood candidate for glaucoma studies. Magnesium hasbeen shown to decrease oxidative stress and apoptosisin retinal tissue and to have retinal ganglion cell sparingeffect. A series of studies has been conducted aboutmagnesium could decrease insulin resistance in diabeticpatients, ease glycemia control and prevent diabetic retinopathy.Magnesium is found to be critically important inmaintaining normal ionic homeostasis of lens. Magnesiumdeficiency has been shown to cause increased lenticularoxidative stress and ionic imbalance in the lens so triggercataractogenesis. J Clin Exp Invest 2013; 4 (2: 244-251Key words: Magnesium, calcium channel blockage,glaucoma, neuroprotection, diabetic retinopathy, cataract

  12. Activation of a cGMP-sensitive calcium-dependent chloride channel may cause transition from calcium waves to whole-cell oscillations in smooth muscle cells

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian; Aalkjær, Christian; Nilsson, Holger;

    2007-01-01

    waves sweeping through the cytoplasm when the SR is stimulated to release calcium. A rise in cyclic guanosine monophosphate (cGMP) leads to the experimentally observed transition from waves to whole-cell calcium oscillations. At the same time membrane potential starts to oscillate and the frequency...... approximately doubles. In this transition, the simulated results point to a key role for a recently discovered cGMP-sensitive calcium-dependent chloride channel. This channel depolarizes the membrane in response to calcium released from the SR. In turn, depolarization causes uniform opening of L-type calcium...... onset of oscillations in membrane potential within the individual cell may underlie sudden intercellular synchronization and the appearance of vasomotion. Key words: Vasomotion, Chloride channel, cGMP, Mathematical model, Calcium waves....

  13. Analytical models of calcium binding in a calcium channel

    International Nuclear Information System (INIS)

    The anomalous mole fraction effect of L-type calcium channels is analyzed using a Fermi like distribution with the experimental data of Almers and McCleskey [J. Physiol. 353, 585 (1984)] and the atomic resolution model of Lipkind and Fozzard [Biochemistry 40, 6786 (2001)] of the selectivity filter of the channel. Much of the analysis is algebraic, independent of differential equations. The Fermi distribution is derived from the configuration entropy of ions and water molecules with different sizes, different valences, and interstitial voids between particles. It allows us to calculate potentials and distances (between the binding ion and the oxygen ions of the glutamate side chains) directly from the experimental data using algebraic formulas. The spatial resolution of these results is comparable with those of molecular models, but of course the accuracy is no better than that implied by the experimental data. The glutamate side chains in our model are flexible enough to accommodate different types of binding ions in different bath conditions. The binding curves of Na+ and Ca2+ for [CaCl2] ranging from 10−8 to 10−2 M with a fixed 32 mM background [NaCl] are shown to agree with published Monte Carlo simulations. The Poisson-Fermi differential equation—that includes both steric and correlation effects—is then used to obtain the spatial profiles of energy, concentration, and dielectric coefficient from the solvent region to the filter. The energy profiles of ions are shown to depend sensitively on the steric energy that is not taken into account in the classical rate theory. We improve the rate theory by introducing a steric energy that lumps the effects of excluded volumes of all ions and water molecules and empty spaces between particles created by Lennard-Jones type and electrostatic forces. We show that the energy landscape varies significantly with bath concentrations. The energy landscape is not constant

  14. Coupling Effect of Ion Channel Clusters on Calcium Signalling

    International Nuclear Information System (INIS)

    Based on a modified intracellular Ca2+ model involving diffusive coupling of two calcium ion channel clusters, the effects of coupling on calcium signalling are numerically investigated. The simulation results indicate that the diffusive coupling of clusters together with internal noise determine the calcium dynamics of single cluster, and for either homogeneous or heterogeneous coupled clusters, the synchronization of clusters, which is important to calcium signalling, is enhanced by the coupling effect

  15. Coupling Effect of Ion Channel Clusters on Calcium Signalling

    Institute of Scientific and Technical Information of China (English)

    TANG Jun; JIA Ya; YI Ming; MA Jun; YU Guang

    2008-01-01

    @@ Based on a modified intracellular Ca2+ model involving diffusive coupling of two calcium ion channel clusters,the effects of coupling on calcium signalling are numerically investigated.The simulation results indicate that the diffusive coupling of clusters together with internal noise determine the calcium dynamics of single cluster,and for either homogeneous or heterogeneous coupled clusters,the synchronization of clusters,which is important to calcium signalling,is enhanced by the coupling effect.

  16. Pharmacokinetic interactions with calcium channel antagonists (Part I).

    Science.gov (United States)

    Schlanz, K D; Myre, S A; Bottorff, M B

    1991-11-01

    Calcium channel antagonists are a diverse class of drugs widely used in combination with other therapeutic agents. The potential exists for many clinically significant pharmacokinetic interactions between these and other concurrently administered drugs. The mechanisms of calcium channel antagonist-induced changes in drug metabolism include altered hepatic blood flow and impaired hepatic enzyme metabolising activity. Increases in serum concentrations and/or reductions in clearance have been reported for several drugs used with a number of calcium channel antagonists. A number of reports and studies of calcium channel antagonist interactions have yielded contradictory results and the clinical significance of pharmacokinetic changes seen with these agents is ill-defined. The first part of this article deals with interactions between calcium antagonists and marker compounds, theophylline, midazolam, lithium, doxorubicin, oral hypoglycaemics and cardiac drugs. PMID:1773549

  17. The impact of calcium current reversal on neurotransmitter release in the electrically stimulated retina

    Science.gov (United States)

    Werginz, Paul; Rattay, Frank

    2016-08-01

    Objective. In spite of intense theoretical and experimental investigations on electrical nerve stimulation, the influence of reversed ion currents on network activity during extracellular stimulation has not been investigated so far. Approach. Here, the impact of calcium current reversal on neurotransmitter release during subretinal stimulation was analyzed with a computational multi-compartment model of a retinal bipolar cell (BC) that was coupled with a four-pool model for the exocytosis from its ribbon synapses. Emphasis was laid on calcium channel dynamics and how these channels influence synaptic release. Main results. Stronger stimulation with anodic pulses caused transmembrane voltages above the Nernst potential of calcium in the terminals and, by this means, forced calcium ions to flow in the reversed direction from inside to the outside of the cell. Consequently, intracellular calcium concentration decreased resulting in a reduced vesicle release or preventing release at all. This mechanism is expected to lead to a pronounced ring-shaped pattern of exocytosis within a group of neighbored BCs when the stronger stimulated cells close to the electrode fail in releasing vesicles. Significance. Stronger subretinal stimulation causes failure of synaptic exocytosis due to reversal of calcium flow into the extracellular space in cells close to the electrode.

  18. Voltage-gated calcium channels and their auxiliary subunits: physiology and pathophysiology and pharmacology.

    Science.gov (United States)

    Dolphin, Annette C

    2016-10-01

    Voltage-gated calcium channels are essential players in many physiological processes in excitable cells. There are three main subdivisions of calcium channel, defined by the pore-forming α1 subunit, the CaV 1, CaV 2 and CaV 3 channels. For all the subtypes of voltage-gated calcium channel, their gating properties are key for the precise control of neurotransmitter release, muscle contraction and cell excitability, among many other processes. For the CaV 1 and CaV 2 channels, their ability to reach their required destinations in the cell membrane, their activation and the fine tuning of their biophysical properties are all dramatically influenced by the auxiliary subunits that associate with them. Furthermore, there are many diseases, both genetic and acquired, involving voltage-gated calcium channels. This review will provide a general introduction and then concentrate particularly on the role of auxiliary α2 δ subunits in both physiological and pathological processes involving calcium channels, and as a therapeutic target.

  19. Redox control of calcium channels: from mechanisms to therapeutic opportunities.

    Science.gov (United States)

    Hool, Livia C; Corry, Ben

    2007-04-01

    Calcium plays an integral role in cellular function. It is a well-recognized second messenger necessary for signaling cellular responses, but in excessive amounts can be deleterious to function, causing cell death. The main route by which calcium enters the cytoplasm is either from the extracellular compartment or internal addistores via calcium channels. There is good evidence that calcium channels can respond to pharmacological compounds that reduce or oxidize thiol groups on the channel protein. In addition, reactive oxygen species such as hydrogen peroxide and superoxide that can mediate oxidative pathology also mediate changes in channel function via alterations of thiol groups. This review looks at the structure and function of calcium channels, the evidence that changes in cellular redox state mediate changes in channel function, and the role of redox modification of channels in disease processes. Understanding how redox modification of the channel protein alters channel structure and function is providing leads for the design of therapeutic interventions that target oxidative stress responses.

  20. Single molecule microscopy on Store-Operated Calcium channels

    International Nuclear Information System (INIS)

    Store-Operated Calcium Entry is essential for many signaling processes in non-excitable cells. The best studied Store-Operated Calcium current is the Calcium-Release-Activated-Calcium (CRAC) current in T-cells and mast cells, with Orai1 representing the essential pore forming subunit. Functional CRAC channels in store-depleted cells are composed of four Orai1 subunits. However, the stoichiometric composition in resting cells is still discussed controversially: both a tetrameric and a dimeric stoichiometry of resting-state Orai1 have been reported for immobilized or immobile Orai1 proteins. The aim of this thesis was to design a more versatile approach that allows reliable determination of the subunit stoichiometry of mobile Orai1 channels. The motive for this approach is that mobile sub-fractions of the entire Orai1 population provide the cleanest pool of data, devoid of contributions e.g. from immobile Orai1 clusters or Orai1-loaded vesicles attached to the plasma membrane. Moreover, resting-state Orai1 is predominantly mobile, and mobility appears critical for the lateral redistribution which occurs upon store depletion. The method per se is based on single molecule fluorescence microscopy and brightness analysis. Orai1 proteins were fused to a monomeric variant of Green Fluorescent Protein (mGFP) and over-expressed in a human cell line (T24). The 1:1 labeling stoichiometry allows using the brightness of individual Orai1-mGFP channels as a direct measure of the pore stoichiometry. Due to over-expression a potential mixing with endogenous Orai1 can be neglected. However, over-expression of Orai1-mGFP results in channel densities that are too high to allow for resolving single channels using diffraction limited optical microscopy. In order to overcome this challenge, I developed an experimental strategy that allows reduction of the density of actively fluorescent Orai1-mGFP channels without altering the labeling stoichiometry. In order to reduce the surface density

  1. Calcium channels in the brain as targets for the calcium-channel modulators used in the treatment of neurological disorders

    NARCIS (Netherlands)

    Peters, Thies; WILFFERT, B; VANHOUTTE, PM; VANZWIETEN, PA

    1991-01-01

    Recent investigations of calcium channels in brain cells by voltage-clamp techniques have revealed that, in spite of electrophysiological similarities, the pharmacological properties of these channels differ considerably from channels in peripheral tissues, e.g., heart and smooth muscle. Therefore,

  2. [Model of the selective calcium channel of characean algae].

    Science.gov (United States)

    Lunevskiĭ, V Z; Zherelova, O M; Aleksandrov, A A; Vinokurov, M G; Berestovskiĭ, G N

    1980-01-01

    The present work was intended to further investigate the selective filter of calcium channel on both a cell membrane and reconstructed channels. For the studies on cell membranes, an inhibitor of chloride channels was chosen (ethacrynic acid) to pass currents only through the calcium channels. On both the cells and reconstructed channels, permeability of ions of different crystal radii and valencies was investigated. The obtained results suggest that the channel represents a wide water pore with a diameter larger than 8 A into which ions go together with the nearest water shell. The values of the maximal currents are given by electrostatic interaction of the ions with the anion center of the channel. A phenomenological two-barrier model of the channel is given which describes the movement of all the ions studied. PMID:6251921

  3. The Use of Calcium Channel Blockers in Skin Diseases

    Directory of Open Access Journals (Sweden)

    Özge Uzun

    2013-05-01

    Full Text Available Calcium channel blockers are a group of drugs often used to treat cardiovascular diseases, such as hypertension, angina, peripheral vascular disorders and some arrhythmias. These drugs may suppress the growth and proliferation of vascular smooth muscle cells and fibroblasts, and inhibit the synthesis of extracellular-matrix proteins,such as collagen, fibronectin, proteoglycans. Some calcium channel blockers also have immunomodulatory or dysregulatory effects on lymphocytes and can suppress superoxide generation and phagocytic activity of neutrophils. Moreover, mast cell degranulation and platelet aggregation may also be impaired. On account of these properties, calcium channel blockers have also been used for the prevention and treatment of various dermatologic diseases. In this review, we evaluated the use of calcium channel blockers in various dermatologic diseases, such as Raynaud’s phenomenon, chilblains, chronic anal fissures, vulvodynia, keloids and burn scars, calcinosis cutis, and leiomyoma.

  4. Intracellular calcium release modulates polycystin-2 trafficking

    Directory of Open Access Journals (Sweden)

    Miyakawa Ayako

    2013-02-01

    Full Text Available Abstract Background Polycystin-2 (PC2, encoded by the gene that is mutated in autosomal dominant polycystic kidney disease (ADPKD, functions as a calcium (Ca2+ permeable ion channel. Considerable controversy remains regarding the subcellular localization and signaling function of PC2 in kidney cells. Methods We investigated the subcellular PC2 localization by immunocytochemistry and confocal microscopy in primary cultures of human and rat proximal tubule cells after stimulating cytosolic Ca2+ signaling. Plasma membrane (PM Ca2+ permeability was evaluated by Fura-2 manganese quenching using time-lapse fluorescence microscopy. Results We demonstrated that PC2 exhibits a dynamic subcellular localization pattern. In unstimulated human or rat proximal tubule cells, PC2 exhibited a cytosolic/reticular distribution. Treatments with agents that in various ways affect the Ca2+ signaling machinery, those being ATP, bradykinin, ionomycin, CPA or thapsigargin, resulted in increased PC2 immunostaining in the PM. Exposing cells to the steroid hormone ouabain, known to trigger Ca2+ oscillations in kidney cells, caused increased PC2 in the PM and increased PM Ca2+ permeability. Intracellular Ca2+ buffering with BAPTA, inositol 1,4,5-trisphosphate receptor (InsP3R inhibition with 2-aminoethoxydiphenyl borate (2-APB or Ca2+/Calmodulin-dependent kinase inhibition with KN-93 completely abolished ouabain-stimulated PC2 translocation to the PM. Conclusions These novel findings demonstrate intracellular Ca2+-dependent PC2 trafficking in human and rat kidney cells, which may provide new insight into cyst formations in ADPKD.

  5. Neuronal modulation of calcium channel activity in cultured rat astrocytes.

    OpenAIRE

    Corvalan, V; Cole, R; de Vellis, J.; Hagiwara, S.

    1990-01-01

    The patch-clamp technique was used to study whether cocultivation of neurons and astrocytes modulates the expression of calcium channel activity in astrocytes. Whole-cell patch-clamp recordings from rat brain astrocytes cocultured with rat embryonic neurons revealed two types of voltage-dependent inward currents carried by Ca2+ and blocked by either Cd2+ or Co2+ that otherwise were not detected in purified astrocytes. This expression of calcium channel activity in astrocytes was neuron depend...

  6. The Use of Calcium Channel Blockers in Skin Diseases

    OpenAIRE

    Özge Uzun; Mualla Polat

    2013-01-01

    Calcium channel blockers are a group of drugs often used to treat cardiovascular diseases, such as hypertension, angina, peripheral vascular disorders and some arrhythmias. These drugs may suppress the growth and proliferation of vascular smooth muscle cells and fibroblasts, and inhibit the synthesis of extracellular-matrix proteins,such as collagen, fibronectin, proteoglycans. Some calcium channel blockers also have immunomodulatory or dysregulatory effects on lymphocytes and can suppress su...

  7. Activation of purified calcium channels by stoichiometric protein phosphorylation

    International Nuclear Information System (INIS)

    Purified dihydropyridine-sensitive calcium channels from rabbit skeletal muscle were reconstituted into phosphatidylcholine vesicles to evaluate the effect of phosphorylation by cyclic AMP-dependent protein kinase (PK-A) on their function. Both the rate and extent of 45Ca2+ uptake into vesicles containing reconstituted calcium channels were increased severalfold after incubation with ATP and PK-A. The degree of stimulation of 45Ca2+ uptake was linearly proportional to the extent of phosphorylation of the alpha 1 and beta subunits of the calcium channel up to a stoichiometry of approximately 1 mol of phosphate incorporated into each subunit. The calcium channels activated by phosphorylation were determined to be incorporated into the reconstituted vesicles in the inside-out orientation and were completely inhibited by low concentrations of dihydropyridines, phenylalkylamines, Cd2+, Ni2+, and Mg2+. The results demonstrate a direct relationship between PK-A-catalyzed phosphorylation of the alpha 1 and beta subunits of the purified calcium channel and activation of the ion conductance activity of the dihydropyridine-sensitive calcium channels

  8. The role of calcium in endotoxin-induced release of calcitonin gene-related peptide (CGRP) from rat spinal cord

    Institute of Scientific and Technical Information of China (English)

    唐跃明; 韩启德; 王宪

    1997-01-01

    In the present study, the role of calcium in endotoxin-induced CGRP release was studied. 2 .5-50 μg/mL endotoxin and 1 -10 mmol/L caffeine caused concentration-dependent increase of CGRP release from rat spinal cord in vitro. However, no additive effect could he found when caffeine and endotoxin were concomitantly incubated. By using capsaicin, Ca2+-free medium, Omega-Conotoxin, nifedipine, W-7, ryanodine, MgCl2, Tris-ATP, rutheni-um red, the results indicate that the release of CGRP evoked by endotoxin from the sensory fibers of rat spinal cord is dependent on extracellular calcium. After entering into the cell through the N-type calcium channel, calcium binds to calmodulin, and triggers calcium release from intracellular calcium store by activating the caffeine-sensitive but ryan-odine-insensitive mechanism.

  9. Zebrafish calls for reinterpretation for the roles of P/Q calcium channels in neuromuscular transmission

    OpenAIRE

    Hua WEN; Linhoff, Michael W.; Hubbard, Jeffrey M; Nelson, Nathan R.; Stensland, Donald; Dallman, Julia; Mandel, Gail; Brehm, Paul

    2013-01-01

    A long-held tenet of neuromuscular transmission is that calcium-dependent neurotransmitter release is mediated by N-type calcium channels in frog but P/Q-type channels in mammals. The N-type assignment in frog is based principally on pharmacological sensitivity to ω-conotoxin GVIA. Our studies show that zebrafish neuromuscular transmission is also sensitive to ω-conotoxin GVIA. However, positional cloning of a mutant line with compromised neuromuscular function identified a mutation in a P/Q-...

  10. Treating High Blood Pressure: Is a Calcium Channel Blocker Drug Right for You?

    Science.gov (United States)

    ... Blood Pressure: Is a Calcium Channel Blocker Drug Right for You? What are calcium channel blockers? Calcium ... talk with your doctor about which drugs are right for you. If your blood pressure is slightly ...

  11. Calcium signaling and T-type calcium channels in cancer cell cycling

    Institute of Scientific and Technical Information of China (English)

    James T Taylor; Xiang-Bin Zeng; Jonathan E Pottle; Kevin Lee; Alun R Wang; Stephenie G Yi; Jennifer A S Scruggs; Suresh S Sikka; Ming Li

    2008-01-01

    Regulation of intracellular calcium is an important signaling mechanism for cell proliferation in both normal and cancerous cells. In normal epithelial cells,free calcium concentration is essential for cells to enter and accomplish the S phase and the M phase of the cell cycle. In contrast, cancerous cells can pass these phases of the cell cycle with much lower cytoplasmic free calcium concentrations, indicating an alternative mechanism has developed for fulfilling the intracellular calcium requirement for an increased rate of DNA synthesis and mitosis of fast replicating cancerous cells. The detailed mechanism underlying the altered calcium loading pathway remains unclear;however, there is a growing body of evidence that suggests the T-type Ca2+ channel is abnormally expressed in cancerous cells and that blockade of these channels may reduce cell proliferation in addition to inducing apoptosis. Recent studies also show that the expression of T-type Ca2+ channels in breast cancer cells is proliferation state dependent, i.e. the channels are expressed at higher levels during the fast-replication period, and once the cells are in a non-proliferation state, expression of this channel isminimal. Therefore, selectively blocking calcium entry into cancerous cells may be a valuable approach for preventing tumor growth. Since T-type Ca2+ channels are not expressed in epithelial cells, selective T-type Ca2+ channel blockers may be useful in the treatment of certain types of cancers.

  12. The cardiac L-type calcium channel distal carboxy terminus autoinhibition is regulated by calcium.

    Science.gov (United States)

    Crump, Shawn M; Andres, Douglas A; Sievert, Gail; Satin, Jonathan

    2013-02-01

    The L-type calcium channel (LTCC) provides trigger Ca(2+) for sarcoplasmic reticulum Ca-release, and LTCC function is influenced by interacting proteins including the LTCC distal COOH terminus (DCT) and calmodulin. DCT is proteolytically cleaved and reassociates with the LTCC complex to regulate calcium channel function. DCT reduces LTCC barium current (I(Ba,L)) in reconstituted channel complexes, yet the contribution of DCT to LTCC Ca(2+) current (I(Ca,L)) in cardiomyocyte systems is unexplored. This study tests the hypothesis that DCT attenuates cardiomyocyte I(Ca,L). We measured LTCC current and Ca(2+) transients with DCT coexpressed in murine cardiomyocytes. We also heterologously coexpressed DCT and Ca(V)1.2 constructs with truncations corresponding to the predicted proteolytic cleavage site, Ca(V)1.2Δ1801, and a shorter deletion corresponding to well-studied construct, Ca(V)1.2Δ1733. DCT inhibited I(Ba,L) in cardiomyocytes, and in human embryonic kidney (HEK) 293 cells expressing Ca(V)1.2Δ1801 and Ca(V)1.2Δ1733. Ca(2+)-CaM relieved DCT block in cardiomyocytes and HEK cells. The selective block of I(Ba,L) combined with Ca(2+)-CaM effects suggested that DCT-mediated blockade may be relieved under conditions of elevated Ca(2+). We therefore tested the hypothesis that DCT block is dynamic, increasing under relatively low Ca(2+), and show that DCT reduced diastolic Ca(2+) at low stimulation frequencies but spared high frequency Ca(2+) entry. DCT reduction of diastolic Ca(2+) and relief of block at high pacing frequencies and under conditions of supraphysiological bath Ca(2+) suggests that a physiological function of DCT is to increase the dynamic range of Ca(2+) transients in response to elevated pacing frequencies. Our data motivate the new hypothesis that DCT is a native reverse use-dependent inhibitor of LTCC current.

  13. Renin release from permeabilized juxtaglomerular cells is stimulated by chloride but not by low calcium

    DEFF Research Database (Denmark)

    Jensen, B L; Skøtt, O

    1994-01-01

    M]. These maneuvers had no effect on renin release, while 1.5 mM calcium caused a stimulation, which was not inhibited by 50 mM sucrose. Isosmotic increases in the chloride concentration to 25, 60, and 132 mM resulted in prompt stimulations of renin release. Similarly, iodide and nitrate stimulated renin release. We...... of chloride channels followed by a drop in the intracellular chloride concentration. The stimulation caused by the high calcium concentration may be a toxic effect or may be due to stimulation of the fusion between granules and cell membrane in a way analogous to other secretory cells.......The intracellular concentrations of calcium and chloride have been suggested to be involved in the control of renin secretion from juxtaglomerular (JG) cells. We have tested these propositions on permeabilized JG cells. Rat glomeruli with attached JG cells were isolated by the magnetic iron...

  14. Blockade of chloride channels by DIDS stimulates renin release and inhibits contraction of afferent arterioles

    DEFF Research Database (Denmark)

    Jensen, B L; Skøtt, O

    1996-01-01

    or without ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] and DIDS were not additive. In the absence of chloride, basal renin release was suppressed and the stimulatory effect of DIDS was abolished. The DIDS-induced enhancement of renin release was not dependent on bicarbonate...... arterioles with the chloride channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). Renin secretion was equally enhanced by omission of extracellular calcium and by addition of 0.5 mM DIDS. The inhibitory effect of calcium was blocked by DIDS. The stimulatory effects of low calcium [with...

  15. T-Type Calcium Channel: A Privileged Gate for Calcium Entry and Control of Adrenal Steroidogenesis.

    Science.gov (United States)

    Rossier, Michel F

    2016-01-01

    Intracellular calcium plays a crucial role in modulating a variety of functions such as muscle contraction, hormone secretion, gene expression, or cell growth. Calcium signaling has been however shown to be more complex than initially thought. Indeed, it is confined within cell microdomains, and different calcium channels are associated with different functions, as shown by various channelopathies. Sporadic mutations on voltage-operated L-type calcium channels in adrenal glomerulosa cells have been shown recently to be the second most prevalent genetic abnormalities present in human aldosterone-producing adenoma. The observed modification of the threshold of activation of the mutated channels not only provides an explanation for this gain of function but also reminds us on the importance of maintaining adequate electrophysiological characteristics to make channels able to exert specific cellular functions. Indeed, the contribution to steroid production of the various calcium channels expressed in adrenocortical cells is not equal, and the reason has been investigated for a long time. Given the very negative resting potential of these cells, and the small membrane depolarization induced by their physiological agonists, low threshold T-type calcium channels are particularly well suited for responding under these conditions and conveying calcium into the cell, at the right place for controlling steroidogenesis. In contrast, high threshold L-type channels are normally activated by much stronger cell depolarizations. The fact that dihydropyridine calcium antagonists, specific for L-type channels, are poorly efficient for reducing aldosterone secretion either in vivo or in vitro, strongly supports the view that these two types of channels differently affect steroid biosynthesis. Whether a similar analysis is transposable to fasciculata cells and cortisol secretion is one of the questions addressed in the present review. No similar mutations on L-type or T-type channels

  16. T-type calcium channel: a privileged gate for calcium entry and control of adrenal steroidogenesis

    Directory of Open Access Journals (Sweden)

    Michel Florian Rossier

    2016-05-01

    Full Text Available Intracellular calcium plays a crucial role in modulating a variety of functions such as muscle contraction, hormone secretion, gene expression or cell growth. Calcium signaling has been however shown to be more complex than initially thought. Indeed, it is confined within cell microdomains and different calcium channels are associated with different functions, as shown by various channelopathies.Sporadic mutations on voltage-operated L-type calcium channels in adrenal glomerulosa cells have been shown recently to be the second most prevalent genetic abnormalities present in human aldosterone-producing adenoma. The observed modification of the threshold of activation of the mutated channels not only provides an explanation for this gain of function but reminds us on the importance of maintaining adequate electrophysiological characteristics to make channels able to exert specific cellular functions. Indeed, the contribution to steroid production of the various calcium channels expressed in adrenocortical cells is not equal and the reason has been investigated for a long time. Given the very negative resting potential of these cells, and the small membrane depolarization induced by their physiological agonists, low threshold T-type calcium channels are particularly well suited for responding under these conditions and conveying calcium into the cell, at the right place for controlling steroidogenesis. In contrast, high threshold L-type channels are normally activated by much stronger cell depolarizations. The fact that dihydropyridine calcium antagonists, specific for L-type channels, are poorly efficient for reducing aldosterone secretion either in vivo or in vitro, strongly supports the view that these two types of channels differently affect steroid biosynthesis.Whether a similar analysis is transposable to fasciculata cells and cortisol secretion is one of the questions addressed in the present review. No similar mutations on L-type or T

  17. Calcium influx and release mechanism(s) in histamine-induced myometrial contraction in buffaloes.

    Science.gov (United States)

    Sharma, Abhishek; Choudhury, Soumen; Nakade, Udayraj P; Yadav, Rajkumar Singh; Garg, Satish Kumar

    2014-05-01

    The present study was undertaken to characterize the presence of histamine H1R using molecular biology tools and unravel the influx and release mechanism(s) involved in calcium signalling cascades in histamine-induced myometrial contraction in buffaloes. The presence of H1R mRNA transcript and immunoreactive membrane protein in buffalo myometrium was confirmed by RT-PCR and Western blot analysis. Further, histamine produced concentration-dependent (1nM-10μM) contraction in buffalo myometrium with a potency of 7.13±0.11. When myometrial strips were pre-incubated either with Ca(2+) free solution or with nifedipine, a L-type Ca(2+) channel blocker, dose response curve (DRC) of histamine was significantly (PCPA (blocker of sarco-endoplasmic reticulum Ca(2+)-ATPase). Interestingly, following concurrent exposure to U-73122 (a PL-C inhibitor) and nifedipine, the DRC of histamine was significantly (P<0.05) shifted towards left with increase in maximal contraction (126.30±3.36%). Our findings in buffalo uterus thus suggest that influx of extracellular calcium plays a major role in histamine-induced myometrial contraction, while release of intracellular calcium through calcium-release channels of sarcoplasmic reticulum has a minor role. A possible involvement of non-selective cation channels in histamine-induced myometrial contraction cannot be ruled out, and therefore requires further investigations. PMID:24631173

  18. Releasing effects in flame photometry: Determination of calcium

    Science.gov (United States)

    Dinnin, J.I.

    1960-01-01

    Strontium, lanthanum, neodymium, samarium, and yttrium completely release the flame emission of calcium from the depressive effects of sulfate, phosphate, and aluminate. Magnesium, beryllium, barium, and scandium release most of the calcium emission. These cations, when present in high concentration, preferentially form compounds with the depressing anions when the solution is evaporated rapidly in the flame. The mechanism of the interference and releasing effects is explained on the basis of the chemical equilibria in the evaporating droplets of solution and is shown to depend upon the nature of the compounds present in the aqueous phase of the solution. The need for background correction techniques is stressed. The releasing effect is used in the determination of calcium in silicate rocks without the need for separations.

  19. Store-operated calcium channels and pro-inflammatory signals

    Institute of Scientific and Technical Information of China (English)

    Wei-chiao CHANG

    2006-01-01

    In non-excitable cells such as T lymphocytes,hepatocytes,mast cells,endothelia and epithelia,the major pathway for calcium(Ca2+)entry is through store-operated Ca2+ channels in the plasma membrane.These channels are activated by the emptying of intracellular Ca2+ stores,however,neither the gating mechanism nor the downstream targets of these channels has been clear established.Here,I review some of the proposed gating mechanisms of store-operated Ca2+ channels and the functional implications in regulating pro-inflammatory signals.

  20. Cardiac voltage-gated calcium channel macromolecular complexes.

    Science.gov (United States)

    Rougier, Jean-Sébastien; Abriel, Hugues

    2016-07-01

    Over the past 20years, a new field of research, called channelopathies, investigating diseases caused by ion channel dysfunction has emerged. Cardiac ion channels play an essential role in the generation of the cardiac action potential. Investigators have largely determined the physiological roles of different cardiac ion channels, but little is known about the molecular determinants of their regulation. The voltage-gated calcium channel Cav1.2 shapes the plateau phase of the cardiac action potential and allows the influx of calcium leading to cardiomyocyte contraction. Studies suggest that the regulation of Cav1.2 channels is not uniform in working cardiomyocytes. The notion of micro-domains containing Cav1.2 channels and different calcium channel interacting proteins, called macro-molecular complex, has been proposed to explain these observations. The objective of this review is to summarize the currently known information on the Cav1.2 macromolecular complexes in the cardiac cell and discuss their implication in cardiac function and disorder. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel. PMID:26707467

  1. The fourth-generation Calcium channel blocker: Cilnidipine

    OpenAIRE

    Chandra, K. Sarat; Ramesh, G.

    2013-01-01

    Several classes of antihypertensive agents have been in clinical use, including diuretics, α-blockers, β-blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin II type 1 receptor blockers (ARB), and organic calcium channel blockers (CCBs). All these drugs are being currently used in the treatment of Hypertension & various disease conditions of the heart either alone or in combination. Cilnidipine is a new antihypertensive drug distinguished from other L-type Ca2+ channel blocke...

  2. Osteoclast cytosolic calcium, regulated by voltage-gated calcium channels and extracellular calcium, controls podosome assembly and bone resorption

    Science.gov (United States)

    Miyauchi, A.; Hruska, K. A.; Greenfield, E. M.; Duncan, R.; Alvarez, J.; Barattolo, R.; Colucci, S.; Zambonin-Zallone, A.; Teitelbaum, S. L.; Teti, A.

    1990-01-01

    The mechanisms of Ca2+ entry and their effects on cell function were investigated in cultured chicken osteoclasts and putative osteoclasts produced by fusion of mononuclear cell precursors. Voltage-gated Ca2+ channels (VGCC) were detected by the effects of membrane depolarization with K+, BAY K 8644, and dihydropyridine antagonists. K+ produced dose-dependent increases of cytosolic calcium ([Ca2+]i) in osteoclasts on glass coverslips. Half-maximal effects were achieved at 70 mM K+. The effects of K+ were completely inhibited by dihydropyridine derivative Ca2+ channel blocking agents. BAY K 8644 (5 X 10(-6) M), a VGCC agonist, stimulated Ca2+ entry which was inhibited by nicardipine. VGCCs were inactivated by the attachment of osteoclasts to bone, indicating a rapid phenotypic change in Ca2+ entry mechanisms associated with adhesion of osteoclasts to their resorption substrate. Increasing extracellular Ca2+ ([Ca2+]e) induced Ca2+ release from intracellular stores and Ca2+ influx. The Ca2+ release was blocked by dantrolene (10(-5) M), and the influx by La3+. The effects of [Ca2+]e on [Ca2+]i suggests the presence of a Ca2+ receptor on the osteoclast cell membrane that could be coupled to mechanisms regulating cell function. Expression of the [Ca2+]e effect on [Ca2+]i was similar in the presence or absence of bone matrix substrate. Each of the mechanisms producing increases in [Ca2+]i, (membrane depolarization, BAY K 8644, and [Ca2+]e) reduced expression of the osteoclast-specific adhesion structure, the podosome. The decrease in podosome expression was mirrored by a 50% decrease in bone resorptive activity. Thus, stimulated increases of osteoclast [Ca2+]i lead to cytoskeletal changes affecting cell adhesion and decreasing bone resorptive activity.

  3. Oxidative Stress and Maxi Calcium-Activated Potassium (BK Channels

    Directory of Open Access Journals (Sweden)

    Anton Hermann

    2015-08-01

    Full Text Available All cells contain ion channels in their outer (plasma and inner (organelle membranes. Ion channels, similar to other proteins, are targets of oxidative impact, which modulates ion fluxes across membranes. Subsequently, these ion currents affect electrical excitability, such as action potential discharge (in neurons, muscle, and receptor cells, alteration of the membrane resting potential, synaptic transmission, hormone secretion, muscle contraction or coordination of the cell cycle. In this chapter we summarize effects of oxidative stress and redox mechanisms on some ion channels, in particular on maxi calcium-activated potassium (BK channels which play an outstanding role in a plethora of physiological and pathophysiological functions in almost all cells and tissues. We first elaborate on some general features of ion channel structure and function and then summarize effects of oxidative alterations of ion channels and their functional consequences.

  4. Calcium homeostasis and cone signaling are regulated by interactions between calcium stores and plasma membrane ion channels.

    Directory of Open Access Journals (Sweden)

    Tamas Szikra

    Full Text Available Calcium is a messenger ion that controls all aspects of cone photoreceptor function, including synaptic release. The dynamic range of the cone output extends beyond the activation threshold for voltage-operated calcium entry, suggesting another calcium influx mechanism operates in cones hyperpolarized by light. We have used optical imaging and whole-cell voltage clamp to measure the contribution of store-operated Ca(2+ entry (SOCE to Ca(2+ homeostasis and its role in regulation of neurotransmission at cone synapses. Mn(2+ quenching of Fura-2 revealed sustained divalent cation entry in hyperpolarized cones. Ca(2+ influx into cone inner segments was potentiated by hyperpolarization, facilitated by depletion of intracellular Ca(2+ stores, unaffected by pharmacological manipulation of voltage-operated or cyclic nucleotide-gated Ca(2+ channels and suppressed by lanthanides, 2-APB, MRS 1845 and SKF 96365. However, cation influx through store-operated channels crossed the threshold for activation of voltage-operated Ca(2+ entry in a subset of cones, indicating that the operating range of inner segment signals is set by interactions between store- and voltage-operated Ca(2+ channels. Exposure to MRS 1845 resulted in approximately 40% reduction of light-evoked postsynaptic currents in photopic horizontal cells without affecting the light responses or voltage-operated Ca(2+ currents in simultaneously recorded cones. The spatial pattern of store-operated calcium entry in cones matched immunolocalization of the store-operated sensor STIM1. These findings show that store-operated channels regulate spatial and temporal properties of Ca(2+ homeostasis in vertebrate cones and demonstrate their role in generation of sustained excitatory signals across the first retinal synapse.

  5. Heterogeneity of Calcium Channel/cAMP-Dependent Transcriptional Activation.

    Science.gov (United States)

    Kobrinsky, Evgeny

    2015-01-01

    The major function of the voltage-gated calcium channels is to provide the Ca(2+) flux into the cell. L-type voltage-gated calcium channels (Cav1) serve as voltage sensors that couple membrane depolarization to many intracellular processes. Electrical activity in excitable cells affects gene expression through signaling pathways involved in the excitation-transcription (E-T) coupling. E-T coupling starts with activation of the Cav1 channel and results in initiation of the cAMP-response element binding protein (CREB)-dependent transcription. In this review we discuss the new quantitative approaches to measuring E-T signaling events. We describe the use of wavelet transform to detect heterogeneity of transcriptional activation in nuclei. Furthermore, we discuss the properties of discovered microdomains of nuclear signaling associated with the E-T coupling and the basis of the frequency-dependent transcriptional regulation.

  6. Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release

    Directory of Open Access Journals (Sweden)

    Saraiva R.M.

    1997-01-01

    Full Text Available Outward current oscillations associated with transient membrane hyperpolarizations were induced in murine macrophage polykaryons by membrane depolarization in the absence of external Na+. Oscillations corresponded to a cyclic activation of Ca2+-dependent K+ currents (IKCa probably correlated with variations in intracellular Ca2+ concentration. Addition of external Na+ (8 mM immediately abolished the outward current oscillations, suggesting that the absence of the cation is necessary not only for their induction but also for their maintenance. Oscillations were completely blocked by nisoldipine. Ruthenium red and ryanodine reduced the number of outward current cycles in each episode, whereas quercetin prolonged the hyperpolarization 2- to 15-fold. Neither low molecular weight heparin nor the absence of a Na+ gradient across the membrane had any influence on oscillations. The evidence suggests that Ca2+ entry through a pathway sensitive to Ca2+ channel blockers is elicited by membrane depolarization in Na+-free medium and is essential to initiate oscillations, which are also dependent on the cyclic release of Ca2+ from intracellular Ca2+-sensitive stores; Ca2+ ATPase acts by reducing intracellular Ca2+, thus allowing slow deactivation of IKCa. Evidence is presented that neither a Na+/Ca2+ antiporter nor Ca2+ release from IP3-sensitive Ca2+ stores participate directly in the mechanism of oscillation

  7. Pharmacokinetic interactions with calcium channel antagonists (Part II).

    Science.gov (United States)

    Schlanz, K D; Myre, S A; Bottorff, M B

    1991-12-01

    Since calcium channel antagonists are a diverse class of drugs frequently administered in combination with other agents, the potential for clinically significant pharmacokinetic drug interactions exists. These interactions occur most frequently via altered hepatic blood flow and impaired hepatic enzyme activity. Part I of the article, which appeared in the previous issue of the Journal, dealt with interactions between calcium antagonists and marker compounds, theophylline, midazolam, lithium, doxorubicin, oral hypoglycaemics and cardiac drugs. Part II examines interactions with cyclosporin, anaesthetics, carbamazepine and cardiovascular agents. PMID:1782739

  8. Stimulatory effects of maitotoxin on insulin release in insulinoma HIT cells: Role of calcium uptake and phosphoinositide breakdown

    International Nuclear Information System (INIS)

    In hamster insulinoma (HIT) cells, maitotoxin (MTX) induces a time-dependent and concentration-dependent release of insulin that requires the presence of extracellular calcium. The response is nearly completely blocked by cinnarizine and cadmium, but is not inhibited by the L-type calcium channel blocker nifedipine or by manganese. MTX induces 45Ca+ uptake in these cells in a dose-dependent mode, and the uptake is blocked with cinnarizine, nifedipine and cadmium, and is partially inhibited by manganese. MTX induces phosphoinositide breakdown in HIT cells, and the response is partially blocked by cadmium, but is not affected by nifedipine, cinnarizine or manganese. High concentrations of potassium ions also induce insulin release and calcium uptake in HIT cells. Both effects of potassium are blocked partially by nifedipine, cadmium and cinnarizine. High concentrations of potassium do not induce phosphoinositide breakdown in HIT cells. The results suggest that MTX-elicited release of insulin is attained by two mechanisms: (1) a nifedipine-sensitive action, which results from MTX-induced activation of L-type calcium channels, which can be mimicked with high potassium concentrations; and (2) a nifedipine-insensitive action, which may be initiated by the activation of phosphoinositide breakdown by MTX. Such an activation of phospholipase C would result in the formation of 1,4,5-inositol trisphosphate, a release of intracellular calcium and then release of insulin to the extracellular space. Cinnarizine is proposed to block both MTX-elicited mechanisms, the first by blockade of calcium channels and the second by blocking 1,4,5-inositol trisphosphate-induced release of internal calcium. Either mechanism alone appears capable of eliciting release of insulin

  9. Calcium channel blocking activity of fruits of callistemon citrinus

    International Nuclear Information System (INIS)

    Callistemon citrinus is a plant of family myrtaceae that has a great medicinal importance. Traditional uses of the aerial parts of Callistemon citrinus in ethnic tribal communities are in practice, and very little are known about its importance on scientific grounds. Therefore, the crude methanolic extract of fruits of Callistemon citrinus (C.c) was screened for possible spasmolytic activity on isolated rabbit's jejunum preparations. The extract produced a relaxing effect on spontaneous contraction of rabbit's jejunum. Explaining the mode of action, the extract produced a dose dependent relaxant effect and shifted the calcium response curves to the rightward (EC50 +- SEM = -2.05 +- 0.05 vs. control EC50 +- SEM = -2.5 +- 0.05). The effect of extract was comparable with the effect of verapamil, a standard calcium channel blocker and therefore, the plant specie could be a potential target for isolation of calcium antagonist(s). (author)

  10. Dissolution of the inorganic phase of bone leading to release of calcium regulates osteoclast survival

    DEFF Research Database (Denmark)

    Nielsen, Rasmus H; Karsdal, Morten A; Sørensen, Mette G;

    2007-01-01

    Osteoclasts are the sole cells possessing the ability to resorb calcified bone matrix. This occurs via secretion of hydrochloric acid mediated by the V-ATPase and the chloride channel ClC-7. Loss of acidification leads to osteopetrosis characterized by ablation of bone resorption and increased...... osteoclast numbers, indicating increased life span of the osteoclasts. To investigate the role of the inorganic phase of bone with respect to osteoclast life span, we used the V-ATPase inhibitor bafilomycin and the calcium uptake antagonist ryanodine on human osteoclasts cultured on calcified and decalcified...... bone slices. Bafilomycin inhibited bone resorption and increased osteoclast survival on calcified but not decalcified bones. Ryanodine attenuated calcium uptake and thereby augmented osteoclast survival on calcified bones. In summary, we found that acidification leading to calcium release from bone...

  11. Self-organized models of selectivity in calcium channels

    International Nuclear Information System (INIS)

    The role of flexibility in the selectivity of calcium channels is studied using a simple model with two parameters that accounts for the selectivity of calcium (and sodium) channels in many ionic solutions of different compositions and concentrations using two parameters with unchanging values. We compare the distribution of side chains (oxygens) and cations (Na+ and Ca2+) and integrated quantities. We compare the occupancies of cations Ca2+/Na+ and linearized conductance of Na+. The distributions show a strong dependence on the locations of fixed side chains and the flexibility of the side chains. Holding the side chains fixed at certain predetermined locations in the selectivity filter distorts the distribution of Ca2+ and Na+ in the selectivity filter. However, integrated quantities—occupancy and normalized conductance—are much less sensitive. Our results show that some flexibility of side chains is necessary to avoid obstruction of the ionic pathway by oxygen ions in 'unfortunate' fixed positions. When oxygen ions are mobile, they adjust 'automatically' and move 'out of the way', so they can accommodate the permeable cations in the selectivity filter. Structure is the computed consequence of the forces in this model. The structures are self-organized, at their free energy minimum. The relationship of ions and side chains varies with an ionic solution. Monte Carlo simulations are particularly well suited to compute induced-fit, self-organized structures because the simulations yield an ensemble of structures near their free energy minimum. The exact location and mobility of oxygen ions has little effect on the selectivity behavior of calcium channels. Seemingly, nature has chosen a robust mechanism to control selectivity in calcium channels: the first-order determinant of selectivity is the density of charge in the selectivity filter. The density is determined by filter volume along with the charge and excluded volume of

  12. Deoxynivalenol (Vomitoxin)-Induced Cholecystokinin and Glucagon-Like Peptide-1 Release in the STC-1 Enteroendocrine Cell Model Is Mediated by Calcium-Sensing Receptor and Transient Receptor Potential Ankyrin-1 Channel.

    Science.gov (United States)

    Zhou, Hui-Ren; Pestka, James J

    2015-06-01

    Food refusal is a hallmark of exposure of experimental animals to the trichothecene mycotoxin deoxynivalenol (DON), a common foodborne contaminant. Although studies in the mouse suggest that DON suppresses food intake by aberrantly inducing the release of satiety hormones from enteroendocrine cells (EECs) found in the gut epithelium, the underlying mechanisms for this effect are not understood. To address this gap, we employed the murine neuroendocrine tumor STC-1 cell line, a widely used EEC model, to test the hypothesis that DON-induced hormone exocytosis is mediated by G protein-coupled receptor (GPCR)-mediated Ca(2+) signaling. The results indicate for the first time that DON elicits Ca(2)-dependent secretion of cholecystokinin (CCK) and glucagon-like peptide-1(7-36) amide (GLP-1), hormones that regulate food intake and energy homeostasis and that are products of 2 critical EEC populations--I cells of the small intestine and L cells of the large intestine, respectively. Furthermore, these effects were mediated by the GPCR Ca(2+)-sensing receptor (CaSR) and involved the following serial events: (1)PLC-mediated activation of the IP3 receptor and mobilization of intracellular Ca(2+) stores, (2) activation of transient receptor potential melastatin-5 ion channel and resultant L-type voltage-sensitive Ca(2+) channel-facilitated extracellular Ca(2+) entry, (3) amplification of extracellular Ca(2+) entry by transient receptor potential ankyrin-1 channel activation, and finally (4) Ca(2+)-driven CCK and GLP-1 excytosis. These in vitro findings provide a foundation for future investigation of mechanisms by which DON and other trichothecenes modulate EEC function in ex vivo and in vivo models. PMID:25787141

  13. Clofazimine inhibits human Kv1.3 potassium channel by perturbing calcium oscillation in T lymphocytes.

    Directory of Open Access Journals (Sweden)

    Yunzhao R Ren

    Full Text Available The Kv1.3 potassium channel plays an essential role in effector memory T cells and has been implicated in several important autoimmune diseases including multiple sclerosis, psoriasis and type 1 diabetes. A number of potent small molecule inhibitors of Kv1.3 channel have been reported, some of which were found to be effective in various animal models of autoimmune diseases. We report herein the identification of clofazimine, a known anti-mycobacterial drug, as a novel inhibitor of human Kv1.3. Clofazimine was initially identified as an inhibitor of intracellular T cell receptor-mediated signaling leading to the transcriptional activation of human interleukin-2 gene in T cells from a screen of the Johns Hopkins Drug Library. A systematic mechanistic deconvolution revealed that clofazimine selectively blocked the Kv1.3 channel activity, perturbing the oscillation frequency of the calcium-release activated calcium channel, which in turn led to the inhibition of the calcineurin-NFAT signaling pathway. These effects of clofazimine provide the first line of experimental evidence in support of a causal relationship between Kv1.3 and calcium oscillation in human T cells. Furthermore, clofazimine was found to be effective in blocking human T cell-mediated skin graft rejection in an animal model in vivo. Together, these results suggest that clofazimine is a promising immunomodulatory drug candidate for treating a variety of autoimmune disorders.

  14. Effect of pulse magnetic field stimulation on calcium channel current

    International Nuclear Information System (INIS)

    This study aimed to investigate the effect of low frequency and high amplitude pulse magnetic field (PMF) on Calcium ion channel current of cells. Measurements were done on the Human Embryonic Kidney 293 cells (HEK 293), which have only Calcium ion channels functioning. The whole cell current was measured by patch clamp method, with the clamped voltage ramping from −90 mV to +50 mV across the cell membrane. A PMF was generated by a 400-turn coil connected to a pulse current generator. The frequency of the pulse was 7 Hz, the width of the pulse was 3 ms, and the amplitude of the pulse, or the flux density, was ranging from 6 to 25 mT. The results showed that the profile of the whole cell Calcium channel current could be modified by the PMF. With the PMF applied, the phase shifting occurred: the onset of the channel opening took place several mili-seconds earlier than that without the PWF and correspondingly, the whole cell current reached its maximum earlier, and the current returned back to zero earlier as well. When the PWF was stopped, these effects persisted for a period of time, and then the current profile “recovered” to its original appearance. The decrease of the onset time and peak current time could be due to the local electric potential induced by the PWF and the direct interaction between PMF and ion channels/ions. The exact mechanisms of the observed effects of PMF on the cell are still unknown and need to be further studied.

  15. T-type calcium channels in neuropathic pain.

    Science.gov (United States)

    Bourinet, Emmanuel; Francois, Amaury; Laffray, Sophie

    2016-02-01

    Pain is a quite frequent complaint accompanying numerous pathologies. Among these pathological cases, numerous neuropathies are retrieved with identified etiologies (chemotherapies, diabetes, surgeries…) and also more diffuse syndromes such as fibromyalgia. More broadly, pain is one of the first consequences of most inherited diseases. Despite its importance for the quality of life, current pain management is limited to drugs that are either old or with a limited efficacy or that possess a bad risk benefit ratio. As no new pharmacological concept has led to new analgesics in the last decades, the discovery of new medications is needed, and to this aim, the identification of new druggable targets in pain transmission is a first step. Therefore, studies of ion channels in pain pathways are extremely active. This is particularly true with ion channels in peripheral sensory neurons in dorsal root ganglia known how to express unique sets of these channels. Moreover, both spinal and supraspinal levels are clearly important in pain modulation. Among these ion channels, we and others revealed the important role of low voltage-gated calcium channels in cellular excitability in different steps of the pain pathways. These channels, by being activated nearby resting membrane potential, have biophysical characteristics suited to facilitate action potential generation and rhythmicity. In this review, we will present the current knowledge on the role of these channels in the perception and modulation of pain. PMID:26785151

  16. Modulation of elementary calcium release mediates a transition from puffs to waves in an IP3R cluster model.

    Directory of Open Access Journals (Sweden)

    Martin Rückl

    2015-01-01

    Full Text Available The oscillating concentration of intracellular calcium is one of the most important examples for collective dynamics in cell biology. Localized releases of calcium through clusters of inositol 1,4,5-trisphosphate receptor channels constitute elementary signals called calcium puffs. Coupling by diffusing calcium leads to global releases and waves, but the exact mechanism of inter-cluster coupling and triggering of waves is unknown. To elucidate the relation of puffs and waves, we here model a cluster of IP3R channels using a gating scheme with variable non-equilibrium IP3 binding. Hybrid stochastic and deterministic simulations show that puffs are not stereotyped events of constant duration but are sensitive to stimulation strength and residual calcium. For increasing IP3 concentration, the release events become modulated at a timescale of minutes, with repetitive wave-like releases interspersed with several puffs. This modulation is consistent with experimental observations we present, including refractoriness and increase of puff frequency during the inter-wave interval. Our results suggest that waves are established by a random but time-modulated appearance of sustained release events, which have a high potential to trigger and synchronize activity throughout the cell.

  17. Crystal structure of the epithelial calcium channel TRPV6.

    Science.gov (United States)

    Saotome, Kei; Singh, Appu K; Yelshanskaya, Maria V; Sobolevsky, Alexander I

    2016-06-23

    Precise regulation of calcium homeostasis is essential for many physiological functions. The Ca(2+)-selective transient receptor potential (TRP) channels TRPV5 and TRPV6 play vital roles in calcium homeostasis as Ca(2+) uptake channels in epithelial tissues. Detailed structural bases for their assembly and Ca(2+) permeation remain obscure. Here we report the crystal structure of rat TRPV6 at 3.25 Å resolution. The overall architecture of TRPV6 reveals shared and unique features compared with other TRP channels. Intracellular domains engage in extensive interactions to form an intracellular 'skirt' involved in allosteric modulation. In the K(+) channel-like transmembrane domain, Ca(2+) selectivity is determined by direct coordination of Ca(2+) by a ring of aspartate side chains in the selectivity filter. On the basis of crystallographically identified cation-binding sites at the pore axis and extracellular vestibule, we propose a Ca(2+) permeation mechanism. Our results provide a structural foundation for understanding the regulation of epithelial Ca(2+) uptake and its role in pathophysiology. PMID:27296226

  18. Synthesis of carbon-11 labelled calcium channel antagonists

    International Nuclear Information System (INIS)

    A useful synthetic approach to carbon-11 labelled 1,4-dihydropyridines is described. Carbon-11 labelled calcium channel antagonists 11C-Nifedipine, 11C-Nisoldipine, 11C-nitrendipine and 11C-CF3-Nifedipine were synthesized by a modified Hantzsch method using protected carboxy functions. Deprotection of the carboxylic acids by alkaline hydrolysis followed by conversion into the corresponding potassium salts and subsequent methylation with 11CH3I produced the labelled compounds in very good chemical and radiochemical yields (94%). (author)

  19. The action of calcium channel blockers on recombinant L-type calcium channel alpha1-subunits.

    OpenAIRE

    Morel, Nicole; Buryi, V; Feron, Olivier; Gomez, J. P.; Christen, M O; Godfraind, Theophile

    1998-01-01

    1. CHO cells expressing the alpha(1C-a) subunit (cardiac isoform) and the alpha(1C-b) subunit (vascular isoform) of the voltage-dependent L-type Ca2+ channel were used to investigate whether tissue selectivity of Ca2+ channel blockers could be related to different affinities for alpha1C isoforms. 2. Inward current evoked by the transfected alpha1 subunit was recorded by the patch-clamp technique in the whole-cell configuration. 3. Neutral dihydropyridines (nifedipine, nisoldipine, (+)-PN200-1...

  20. Interaction of H2S with Calcium Permeable Channels and Transporters

    Directory of Open Access Journals (Sweden)

    Weihua Zhang

    2015-01-01

    Full Text Available A growing amount of evidence has suggested that hydrogen sulfide (H2S, as a gasotransmitter, is involved in intensive physiological and pathological processes. More and more research groups have found that H2S mediates diverse cellular biological functions related to regulating intracellular calcium concentration. These groups have demonstrated the reciprocal interaction between H2S and calcium ion channels and transporters, such as L-type calcium channels (LTCC, T-type calcium channels (TTCC, sodium/calcium exchangers (NCX, transient receptor potential (TRP channels, β-adrenergic receptors, and N-methyl-D-aspartate receptors (NMDAR in different cells. However, the understanding of the molecular targets and mechanisms is incomplete. Recently, some research groups demonstrated that H2S modulates the activity of calcium ion channels through protein S-sulfhydration and polysulfide reactions. In this review, we elucidate that H2S controls intracellular calcium homeostasis and the underlying mechanisms.

  1. Dopamine receptors on adrenal chromaffin cells modulate calcium uptake and catecholamine release

    Energy Technology Data Exchange (ETDEWEB)

    Bigornia, L.; Suozzo, M.; Ryan, K.A.; Napp, D.; Schneider, A.S.

    1988-10-01

    The presence of dopamine-containing cells in sympathetic ganglia, i.e., small, intensely fluorescent cells, has been known for some time. However, the role of dopamine as a peripheral neurotransmitter and its mechanism of action are not well understood. Previous studies have demonstrated the presence of D2 dopamine receptors on the surface of bovine adrenal chromaffin cells using radioligand binding methods and dopamine receptor inhibition of catecholamine release from perfused adrenal glands. In the present study, we provide evidence confirming a role of dopamine receptors as inhibitory modulators of adrenal catecholamine release from bovine chromaffin cell cultures and further show that the mechanism of modulation involves inhibition of stimulated calcium uptake. Apomorphine gave a dose-dependent inhibition (IC50 = 1 microM) of 45Ca2+ uptake stimulated by either nicotine (10 microM) or membrane depolarization with an elevated K+ level (60 mM). This inhibition was reversed by a series of specific (including stereospecific) dopamine receptor antagonists: haloperidol, spiperone, sulpiride, and (+)-butaclamol, but not (-)-butaclamol. In addition, the calcium channel agonist Bay K 8644 was used to stimulate uptake of 45Ca2+ into chromaffin cells, and this uptake was also inhibited by the dopamine receptor agonist apomorphine. The combined results suggest that dopamine receptors on adrenal chromaffin cells alter Ca2+ channel conductance, which, in turn, modulates catecholamine release.

  2. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

    OpenAIRE

    Gerald W Zamponi; Striessnig, Joerg; Koschak, Alexandra; Dolphin, Annette C.

    2015-01-01

    Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type ...

  3. Trypsin-Sensitive, Rapid Inactivation of a Calcium-Activated Potassium Channel

    Science.gov (United States)

    Solaro, Christopher R.; Lingle, Christopher J.

    1992-09-01

    Most calcium-activated potassium channels couple changes in intracellular calcium to membrane excitability by conducting a current with a probability that depends directly on submembrane calcium concentration. In rat adrenal chromaffin cells, however, a large conductance, voltage- and calcium-activated potassium channel (BK) undergoes rapid inactivation, suggesting that this channel has a physiological role different than that of other BK channels. The inactivation of the BK channel, like that of the voltage-gated Shaker B potassium channel, is removed by trypsin digestion and channels are blocked by the Shaker B amino-terminal inactivating domain. Thus, this BK channel shares functional and possibly structural homologies with other inactivating voltage-gated potassium channels.

  4. Voltage-Gated Calcium Channel Antagonists and Traumatic Brain Injury

    Directory of Open Access Journals (Sweden)

    Bruce Lyeth

    2013-06-01

    Full Text Available Traumatic brain injury (TBI is a leading cause of death and disability in the United States. Despite more than 30 years of research, no pharmacological agents have been identified that improve neurological function following TBI. However, several lines of research described in this review provide support for further development of voltage gated calcium channel (VGCC antagonists as potential therapeutic agents. Following TBI, neurons and astrocytes experience a rapid and sometimes enduring increase in intracellular calcium ([Ca2+]i. These fluxes in [Ca2+]i drive not only apoptotic and necrotic cell death, but also can lead to long-term cell dysfunction in surviving cells. In a limited number of in vitro experiments, both L-type and N-type VGCC antagonists successfully reduced calcium loads as well as neuronal and astrocytic cell death following mechanical injury. In rodent models of TBI, administration of VGCC antagonists reduced cell death and improved cognitive function. It is clear that there is a critical need to find effective therapeutics and rational drug delivery strategies for the management and treatment of TBI, and we believe that further investigation of VGCC antagonists should be pursued before ruling out the possibility of successful translation to the clinic.

  5. Inhibition of Voltage-Gated Calcium Channels by RGK Proteins.

    Science.gov (United States)

    Buraei, Zafir; Yang, Jian

    2015-01-01

    Due to their essential biological roles, voltage-gated calcium channels (VGCCs) are regulated by a myriad of molecules and mechanisms. Fifteen years ago, RGK proteins were discovered to bind the VGCC β subunit (Cavβ) and potently inhibit high-voltage activated Ca(2+) channels. RGKs (Rad, Rem, Rem2 and Gem/Kir) are a family of monomeric small GTPases belonging to the superfamily of Ras GTPases. They exert dual inhibitory effects on VGCCs, decreasing surface expression and suppressing surface channels through immobilization of the voltage sensor or reduction of channel open probability. While Cavβ is required for all forms of RGK inhibition, not all inhibition is mediated by the RGK-Cavβ interaction. Some RGK proteins also interact directly with the pore-forming α1 subunit of some types of VGCCs (Cavα1). Importantly, RGK proteins tonically inhibit VGCCs in native cells, regulating cardiac and neural functions. This minireview summarizes the mechanisms, molecular determinants, and physiological impact of RGK inhibition of VGCCs. PMID:25966691

  6. The action of calcium channel blockers on recombinant L-type calcium channel α1-subunits

    Science.gov (United States)

    Morel, Nicole; Buryi, Vitali; Feron, Olivier; Gomez, Jean-Pierre; Christen, Marie-Odile; Godfraind, Théophile

    1998-01-01

    CHO cells expressing the α1C-a subunit (cardiac isoform) and the α1C-b subunit (vascular isoform) of the voltage-dependent L-type Ca2+ channel were used to investigate whether tissue selectivity of Ca2+ channel blockers could be related to different affinities for α1C isoforms.Inward current evoked by the transfected α1 subunit was recorded by the patch-clamp technique in the whole-cell configuration.Neutral dihydropyridines (nifedipine, nisoldipine, (+)-PN200-110) were more potent inhibitors of α1C-b-subunit than of α1C-a-subunit. This difference was more marked at a holding potential of −100 mV than at −50 mV. SDZ 207-180 (an ionized dihydropyridine) exhibited the same potency on the two isoforms.Pinaverium (ionized non-dihydropyridine derivative) was 2 and 4 fold more potent on α1C-a than on α1C-b subunit at Vh of −100 mV and −50 mV, respectively. Effects of verapamil were identical on the two isoforms at both voltages.[3H]-(+)-PN 200-110 binding experiments showed that neutral dihydropyridines had a higher affinity for the α1C-b than for the α1C-a subunit. SDZ 207-180 had the same affinity for the two isoforms and pinaverium had a higher affinity for the α1C-a subunit than for the α1C-b subunit.These results indicate marked differences among Ca2+ channel blockers in their selectivity for the α1C-a and α1C-b subunits of the Ca2+ channel. PMID:9846638

  7. The action of calcium channel blockers on recombinant L-type calcium channel alpha1-subunits.

    Science.gov (United States)

    Morel, N; Buryi, V; Feron, O; Gomez, J P; Christen, M O; Godfraind, T

    1998-11-01

    1. CHO cells expressing the alpha(1C-a) subunit (cardiac isoform) and the alpha(1C-b) subunit (vascular isoform) of the voltage-dependent L-type Ca2+ channel were used to investigate whether tissue selectivity of Ca2+ channel blockers could be related to different affinities for alpha1C isoforms. 2. Inward current evoked by the transfected alpha1 subunit was recorded by the patch-clamp technique in the whole-cell configuration. 3. Neutral dihydropyridines (nifedipine, nisoldipine, (+)-PN200-110) were more potent inhibitors of alpha(1C-)b-subunit than of alpha(1C-a)-subunit. This difference was more marked at a holding potential of -100 mV than at -50 mV. SDZ 207-180 (an ionized dihydropyridine) exhibited the same potency on the two isoforms. 4. Pinaverium (ionized non-dihydropyridine derivative) was 2 and 4 fold more potent on alpha(1C-a) than on alpha(1C-b) subunit at Vh of -100 mV and -50 mV, respectively. Effects of verapamil were identical on the two isoforms at both voltages. 5. [3H]-(+)-PN 200-110 binding experiments showed that neutral dihydropyridines had a higher affinity for the alpha(1C-b) than for the alpha(1C-a) subunit. SDZ 207-180 had the same affinity for the two isoforms and pinaverium had a higher affinity for the alpha(1C-a) subunit than for the alpha(1C-b) subunit. 6. These results indicate marked differences among Ca2+ channel blockers in their selectivity for the alpha(1C-a) and alpha(1C-b) subunits of the Ca2+ channel. PMID:9846638

  8. Regulation of dendritic calcium release in striatal spiny projection neurons

    OpenAIRE

    Plotkin, Joshua L.; Shen, Weixing; Rafalovich, Igor; Sebel, Luke E.; Day, Michelle; Chan, C. Savio; Surmeier, D. James

    2013-01-01

    The induction of corticostriatal long-term depression (LTD) in striatal spiny projection neurons (SPNs) requires coactivation of group I metabotropic glutamate receptors (mGluRs) and L-type Ca2+ channels. This combination leads to the postsynaptic production of endocannabinoids that act presynaptically to reduce glutamate release. Although the necessity of coactivation is agreed upon, why it is necessary in physiologically meaningful settings is not. The studies described here attempt to answ...

  9. Asenapine modulates nitric oxide release and calcium movements in cardiomyoblasts

    Directory of Open Access Journals (Sweden)

    Elena Grossini

    2016-01-01

    Full Text Available Objective: To examine the effects of asenapine on nitric oxide (NO release and Ca2+ transients in H9C2 cell line, which were either subjected to peroxidation or not. Materials and Methods: H9C2 were treated with asenapine alone or in presence of intracellular kinase blockers, serotoninergic and dopaminergic antagonists, and voltage Ca2+ channels inhibitors. Experiments were also performed in H9C2 treated with hydrogen peroxide. NO release and intracellular Ca2+ were measured through specific probes. Results: In H9C2, asenapine differently modulated NO release and Ca2+ movements depending on peroxidative condition. The Ca2+ pool mobilized by asenapine mainly originated from the extracellular space and was slightly affected by thapsigargin. Moreover, the effects of asenapine were reduced or prevented by kinases blockers, dopaminergic and serotoninergic receptors inhibitors, and voltage Ca2+ channels blockers.Conclusions: On the basis of our findings, we can conclude that asenapine by interacting with its specific receptors, exerts dual effects on NO release and Ca2+ homeostasis in H9C2; this would be of particular clinical relevance when considering their role in cardiac function modulation.

  10. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus.

    Science.gov (United States)

    Chameau, Pascal; Qin, Yongjun; Spijker, Sabine; Smit, August Benjamin; Smit, Guus; Joëls, Marian

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover, we addressed the putative gene targets that eventually lead to the enhanced calcium currents. Electrophysiological recordings were performed in nucleated patches that allow excellent voltage control. Calcium currents in these patches almost exclusively involve N- and L-type channels. We found that L- but not N-type calcium currents were largely enhanced after treatment with a high dose of corticosterone sufficient to activate glucocorticoid receptors. Voltage dependency and kinetic properties of the currents were unaffected by the hormone. Nonstationary noise analysis suggests that the increased current is not caused by a larger unitary conductance, but rather to a doubling of the number of functional channels. Quantitative real-time PCR revealed that transcripts of the Ca(v)1 subunits encoding for the N- or L-type calcium channels are not upregulated in the mouse CA1 area; instead, a strong, direct, and consistent upregulation of the beta4 subunit was observed. This indicates that the corticosteroid-induced increase in number of L-type calcium channels is not caused by a simple transcriptional regulation of the pore-forming subunit of the channels.

  11. Evaluation of calcium ion, hydroxyl ion release and pH levels in various calcium hydroxide based intracanal medicaments: An in vitro study

    OpenAIRE

    Punit Fulzele; Sudhindra Baliga; Nilima Thosar; Debaprya Pradhan

    2011-01-01

    Aims: Evaluation of calcium ion and hydroxyl ion release and pH levels in various calcium hydroxide based intracanal medicaments. Objective: The purpose of this study was to evaluate calcium and hydroxyl ion release and pH levels of calcium hydroxide based products, namely, RC Cal, Metapex, calcium hydroxide with distilled water, along with the new gutta-percha points with calcium hydroxide. Materials and Methods: The materials were inserted in polyethylene tubes and immersed in deionized wat...

  12. Store-operated channels regulate intracellular calcium in mammalian rods.

    Science.gov (United States)

    Molnar, Tünde; Barabas, Peter; Birnbaumer, Lutz; Punzo, Claudio; Kefalov, Vladimir; Križaj, David

    2012-08-01

    Exposure to daylight closes cyclic nucleotide-gated (CNG) and voltage-operated Ca(2+) -permeable channels in mammalian rods. The consequent lowering of the cytosolic calcium concentration ([Ca(2+)](i)), if protracted, can contribute to light-induced damage and apoptosis in these cells. We here report that mouse rods are protected against prolonged lowering of [Ca(2+)](i) by store-operated Ca(2+) entry (SOCE). Ca(2+) stores were depleted in Ca(2+)-free saline supplemented with the endoplasmic reticulum (ER) sequestration blocker cyclopiazonic acid. Store depletion elicited [Ca(2+)](i) signals that exceeded baseline [Ca(2+)](i) by 5.9 ± 0.7-fold and were antagonized by an inhibitory cocktail containing 2-APB, SKF 96365 and Gd(3+). Cation influx through SOCE channels was sufficient to elicit a secondary activation of L-type voltage-operated Ca2+ entry. We also found that TRPC1, the type 1 canonical mammalian homologue of the Drosophila photoreceptor TRP channel, is predominantly expressed within the outer nuclear layer of the retina. Rod loss in Pde6b(rdl) (rd1), Chx10/Kip1(-/-rdl) and Elovl4(TG2) dystrophic models was associated with ∼70% reduction in Trpc1 mRNA content whereas Trpc1 mRNA levels in rodless cone-full Nrl(-/-) retinas were decreased by ∼50%. Genetic ablation of TRPC1 channels, however, had no effect on SOCE, the sensitivity of the rod phototransduction cascade or synaptic transmission at rod and cone synapses. Thus, we localized two new mechanisms, SOCE and TRPC1, to mammalian rods and characterized the contribution of SOCE to Ca(2+) homeostasis. By preventing the cytosolic [Ca(2+)](i) from dropping too low under sustained saturating light conditions, these signalling pathways may protect Ca(2+)-dependent mechanisms within the ER and the cytosol without affecting normal rod function. PMID:22674725

  13. Huwentoxin-XVI, an analgesic, highly reversible mammalian N-type calcium channel antagonist from Chinese tarantula Ornithoctonus huwena.

    Science.gov (United States)

    Deng, Meichun; Luo, Xuan; Xiao, Yucheng; Sun, Zhenghua; Jiang, Liping; Liu, Zhonghua; Zeng, Xiongzhi; Chen, Hanchun; Tang, Jianhua; Zeng, Weimin; Songping Liang

    2014-04-01

    N-type calcium channels play important roles in the control of neurotransmission release and transmission of pain signals to the central nervous system. Their selective inhibitors are believed to be potential drugs for treating chronic pain. In this study, a novel neurotoxin named Huwentoxin-XVI (HWTX-XVI) specific for N-type calcium channels was purified and characterized from the venom of Chinese tarantula Ornithoctonus huwena. HWTX-XVI is composed of 39 amino acid residues including six cysteines that constitute three disulfide bridges. HWTX-XVI could almost completely block the twitch response of rat vas deferens to low-frequency electrical stimulation. Electrophysiological assay indicated that HWTX-XVI specifically inhibited N-type calcium channels in rat dorsal root ganglion cells (IC50 ∼60 nM). The inhibitory effect of HWTX-XVI on N-type calcium channel currents was dose-dependent and similar to that of CTx-GVIA and CTx-MVIIA. However, the three peptides exhibited markedly different degrees of reversibility after block. The toxin had no effect on voltage-gated T-type calcium channels, potassium channels or sodium channels. Intraperitoneal injection of the toxin HWTX-XVI to rats elicited significant analgesic responses to formalin-induced inflammation pain. Toxin treatment also changed withdrawal latency in hot plate tests. Intriguingly, we found that intramuscular injection of the toxin reduced mechanical allodynia induced by incisional injury in Von Frey test. Thus, our findings suggest that the analgesic potency of HWTX-XVI and its greater reversibility could contribute to the design of a novel potential analgesic agent with high potency and low side effects. PMID:24467846

  14. Differential calcium signaling mediated by voltage-gated calcium channels in rat retinal ganglion cells and their unmyelinated axons.

    Directory of Open Access Journals (Sweden)

    Allison Sargoy

    Full Text Available Aberrant calcium regulation has been implicated as a causative factor in the degeneration of retinal ganglion cells (RGCs in numerous injury models of optic neuropathy. Since calcium has dual roles in maintaining homeostasis and triggering apoptotic pathways in healthy and injured cells, respectively, investigation of voltage-gated Ca channel (VGCC regulation as a potential strategy to reduce the loss of RGCs is warranted. The accessibility and structure of the retina provide advantages for the investigation of the mechanisms of calcium signalling in both the somata of ganglion cells as well as their unmyelinated axons. The goal of the present study was to determine the distribution of VGCC subtypes in the cell bodies and axons of ganglion cells in the normal retina and to define their contribution to calcium signals in these cellular compartments. We report L-type Ca channel α1C and α1D subunit immunoreactivity in rat RGC somata and axons. The N-type Ca channel α1B subunit was in RGC somata and axons, while the P/Q-type Ca channel α1A subunit was only in the RGC somata. We patch clamped isolated ganglion cells and biophysically identified T-type Ca channels. Calcium imaging studies of RGCs in wholemounted retinas showed that selective Ca channel antagonists reduced depolarization-evoked calcium signals mediated by L-, N-, P/Q- and T-type Ca channels in the cell bodies but only by L-type Ca channels in the axons. This differential contribution of VGCC subtypes to calcium signals in RGC somata and their axons may provide insight into the development of target-specific strategies to spare the loss of RGCs and their axons following injury.

  15. Tailored sequential drug release from bilayered calcium sulfate composites

    International Nuclear Information System (INIS)

    The current standard for treating infected bony defects, such as those caused by periodontal disease, requires multiple time-consuming steps and often multiple procedures to fight the infection and recover lost tissue. Releasing an antibiotic followed by an osteogenic agent from a synthetic bone graft substitute could allow for a streamlined treatment, reducing the need for multiple surgeries and thereby shortening recovery time. Tailorable bilayered calcium sulfate (CS) bone graft substitutes were developed with the ability to sequentially release multiple therapeutic agents. Bilayered composite samples having a shell and core geometry were fabricated with varying amounts (1 or 10 wt.%) of metronidazole-loaded poly(lactic-co-glycolic acid) (PLGA) particles embedded in the shell and simvastatin directly loaded into either the shell, core, or both. Microcomputed tomography showed the overall layered geometry as well as the uniform distribution of PLGA within the shells. Dissolution studies demonstrated that the amount of PLGA particles (i.e., 1 vs. 10 wt.%) had a small but significant effect on the erosion rate (3% vs. 3.4%/d). Mechanical testing determined that introducing a layered geometry had a significant effect on the compressive strength, with an average reduction of 35%, but properties were comparable to those of mandibular trabecular bone. Sustained release of simvastatin directly loaded into CS demonstrated that changing the shell to core volume ratio dictates the duration of drug release from each layer. When loaded together in the shell or in separate layers, sequential release of metronidazole and simvastatin was achieved. By introducing a tunable, layered geometry capable of releasing multiple drugs, CS-based bone graft substitutes could be tailored in order to help streamline the multiple steps needed to regenerate tissue in infected defects. - Highlights: • Bilayered CS composites were fabricated as potential bone graft substitutes. • The shell

  16. Tailored sequential drug release from bilayered calcium sulfate composites

    Energy Technology Data Exchange (ETDEWEB)

    Orellana, Bryan R.; Puleo, David A., E-mail: puleo@uky.edu

    2014-10-01

    The current standard for treating infected bony defects, such as those caused by periodontal disease, requires multiple time-consuming steps and often multiple procedures to fight the infection and recover lost tissue. Releasing an antibiotic followed by an osteogenic agent from a synthetic bone graft substitute could allow for a streamlined treatment, reducing the need for multiple surgeries and thereby shortening recovery time. Tailorable bilayered calcium sulfate (CS) bone graft substitutes were developed with the ability to sequentially release multiple therapeutic agents. Bilayered composite samples having a shell and core geometry were fabricated with varying amounts (1 or 10 wt.%) of metronidazole-loaded poly(lactic-co-glycolic acid) (PLGA) particles embedded in the shell and simvastatin directly loaded into either the shell, core, or both. Microcomputed tomography showed the overall layered geometry as well as the uniform distribution of PLGA within the shells. Dissolution studies demonstrated that the amount of PLGA particles (i.e., 1 vs. 10 wt.%) had a small but significant effect on the erosion rate (3% vs. 3.4%/d). Mechanical testing determined that introducing a layered geometry had a significant effect on the compressive strength, with an average reduction of 35%, but properties were comparable to those of mandibular trabecular bone. Sustained release of simvastatin directly loaded into CS demonstrated that changing the shell to core volume ratio dictates the duration of drug release from each layer. When loaded together in the shell or in separate layers, sequential release of metronidazole and simvastatin was achieved. By introducing a tunable, layered geometry capable of releasing multiple drugs, CS-based bone graft substitutes could be tailored in order to help streamline the multiple steps needed to regenerate tissue in infected defects. - Highlights: • Bilayered CS composites were fabricated as potential bone graft substitutes. • The shell

  17. Influence of slow calcium channel inhibitors on radioprotective effect of phenilephrine

    International Nuclear Information System (INIS)

    Verapamil and cinnarizine decrease radioprotective effect of phenylephrine, but nifedipin (more specific inhibitor of slow calcium channel) dosesn't change it. Consequently, protective effect of phenylephine isn't realized by influx of Ca2+ ions through slow calcium channel

  18. Fabrications of zinc-releasing biocement combining zinc calcium phosphate to calcium phosphate cement.

    Science.gov (United States)

    Horiuchi, Shinya; Hiasa, Masahiro; Yasue, Akihiro; Sekine, Kazumitsu; Hamada, Kenichi; Asaoka, Kenzo; Tanaka, Eiji

    2014-01-01

    Recently, zinc-releasing bioceramics have been the focus of much attention owing to their bone-forming ability. Thus, some types of zinc-containing calcium phosphate (e.g., zinc-doped tricalcium phosphate and zinc-substituted hydroxyapatite) are examined and their osteoblastic cell responses determined. In this investigation, we studied the effects of zinc calcium phosphate (ZCP) derived from zinc phosphate incorporated into calcium phosphate cement (CPC) in terms of its setting reaction and MC3T3-E1 osteoblast-like cell responses. Compositional analysis by powder X-ray diffraction analysis revealed that HAP crystals were precipitated in the CPC containing 10 or 30wt% ZCP after successfully hardening. However, the crystal growth observed by scanning electron microscopy was delayed in the presence of additional ZCP. These findings indicate that the additional zinc inhibits crystal growth and the conversion of CPC to the HAP crystals. The proliferation of the cells and alkaline phosphatase (ALP) activity were enhanced when 10wt% ZCP was added to CPC. Taken together, ZCP added CPC at an appropriate fraction has a potent promotional effect on bone substitute biomaterials. PMID:24090874

  19. Release of Crude Oil from Silica and Calcium Carbonate Surfaces

    DEFF Research Database (Denmark)

    Liu, Xiaoyan; Yan, Wei; Stenby, Erling Halfdan;

    2016-01-01

    on the bare surfaces, surfaces with an adsorbed oil layer, and surfaces after being exposed to aqueous salt solutions. This showed that the silica surface became more hydrophobic after oil adsorption, while the wettability of the calcium carbonate surface was not significantly changed by adsorption of an oil...... oil was investigated by exposing the surfaces with an adsorbed oil layer to a series of NaCl and CaCl2 solutions of decreasing salt concentrations. Here, it was found that the oil release from silica was achieved only by injections of low-salinity solutions, and it is suggested that this observation...... or reduction in ion bridging in the presence of high-salinity NaCl, while the low-salinity effect again was attributed to an expansion of the electrical double layer....

  20. Calcium channel structural determinants of synaptic transmission between identified invertebrate neurons.

    Science.gov (United States)

    Spafford, J David; Munno, David W; Van Nierop, Pim; Feng, Zhong-Ping; Jarvis, Scott E; Gallin, Warren J; Smit, August B; Zamponi, Gerald W; Syed, Naweed I

    2003-02-01

    We report here that unlike what was suggested for many vertebrate neurons, synaptic transmission in Lymnaea stagnalis occurs independent of a physical interaction between presynaptic calcium channels and a functional complement of SNARE proteins. Instead, synaptic transmission in Lymnaea requires the expression of a C-terminal splice variant of the Lymnaea homolog to mammalian N- and P/Q-type calcium channels. We show that the alternately spliced region physically interacts with the scaffolding proteins Mint1 and CASK, and that synaptic transmission is abolished following RNA interference knockdown of CASK or after the injection of peptide sequences designed to disrupt the calcium channel-Mint1 interactions. Our data suggest that Mint1 and CASK may serve to localize the non-L-type channels at the active zone and that synaptic transmission in invertebrate neurons utilizes a mechanism for optimizing calcium entry, which occurs independently of a physical association between calcium channels and SNARE proteins.

  1. Maturation of calcium-dependent GABA, glycine, and glutamate release in the glycinergic MNTB-LSO pathway.

    Directory of Open Access Journals (Sweden)

    Javier Alamilla

    Full Text Available The medial nucleus of the trapezoid body (MNTB is a key nucleus in high-fidelity temporal processing that underlies sound localization in the auditory brainstem. While the glycinergic principal cells of the MNTB project to all primary nuclei of the superior olive, during development the projection from MNTB to the lateral superior olive (LSO is of interest because this immature inhibitory projection is known to undergo tonotopic refinement during an early postnatal period, and because during this period individual MNTB terminals in the LSO transiently release glycine GABA and glutamate. Developmental changes in calcium-dependent release are understood to be required to allow various auditory nuclei to follow high frequency activity; however, little is known about maturation of calcium-dependent release in the MNTB-LSO pathway, which has been presumed to have less stringent requirements for high-fidelity temporal following. In acute brainstem slices of rats age postnatal day 1 to 15 we recorded whole-cell responses in LSO principal neurons to electrical stimulation in the MNTB in order to measure sensitivity to external calcium, the contribution of different voltage-gated calcium channel subtypes to vesicular release, and the maturation of these measures for both GABA/glycine and glutamate transmission. Our results establish that release of glutamate at MNTB-LSO synapses is calcium-dependent. Whereas no significant developmental changes were evident for glutamate release, GABA/glycine release underwent substantial changes over the first two postnatal weeks: soon after birth L-type, N-type, and P/Q-type voltage-gated calcium channels (VGCCs together mediated release, but after hearing onset P/Q-type VGCCs predominated. Blockade of P/Q-type VGCCs reduced the estimated quantal number for GABA/gly and glutamate transmission at P5-8 and the frequency of evoked miniature glycinergic events at P12-15, without apparent effects on spontaneous release of

  2. Effects of calcium channel on 3-morpholinosydnonimine-induced rat hippocampal neuronal apoptosis

    Institute of Scientific and Technical Information of China (English)

    Quanzhong Chang; Shuling Zhang; Yuanyin Zheng; Lijuan Xu; Jinbao Yin; Shining Cai

    2011-01-01

    Previous studies have demonstrated that increased chloride channel activity plays a role in nitric oxide-induced neuronal apoptosis in the rat hippocampus.The present study investigated the effects of the broad-spectrum calcium channel blocker CdC12 on survival rate, percentage of apoptosis, and morphological changes in hippocampal neurons cultured in vitro, as well as the effects of calcium channels on neuronal apoptosis.The chloride channel blockers 4-acetamido-4'-isothiocyanatostilbene-2, 2'-disulfonic acid (SITS) or 4, 4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) increased the survival rate of 3-morpholinosydnonimine (SIN-1)-treated neurons and suppressed SIN-1-induced neuronal apoptosis.The calcium channel blocker CdC12 did not increase the survival rate of neurons and did not affect SIN-1-induced apoptosis or SITS- or DIDS-suppressed neuronal apoptosis.Results demonstrated that calcium channels did not significantly affect neuronal apoptosis.

  3. Deletion of N-type calcium channels alters ethanol reward and reduces ethanol consumption in mice

    OpenAIRE

    Newton, P. M.; Orr, C J; Wallace, M J; Kim, C.; Shin, H. S.; Messing, R O

    2004-01-01

    N-type calcium channels are modulated by acute and chronic ethanol exposure in vitro at concentrations known to affect humans, but it is not known whether N-type channels are important for behavioral responses to ethanol in vivo. Here, we show that in mice lacking functional N-type calcium channels, voluntary ethanol consumption is reduced and place preference is developed only at a low dose of ethanol. The hypnotic effects of ethanol are also substantially diminished, whereas ethanol-induced...

  4. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification.

    Science.gov (United States)

    Alqadah, Amel; Hsieh, Yi-Wen; Schumacher, Jennifer A; Wang, Xiaohong; Merrill, Sean A; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons.

  5. Structure-function of proteins interacting with the alpha1 pore-forming subunit of high voltage-activated calcium channel

    Directory of Open Access Journals (Sweden)

    Alan eNeely

    2014-06-01

    Full Text Available Openings of high-voltage-activated calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, high-voltage-activated calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1 associated with four additional polypeptide chains β, α2, δ and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of high-voltage-activated calcium channels.

  6. Honing in on the ATP Release Channel in Taste Cells.

    Science.gov (United States)

    Medler, Kathryn F

    2015-09-01

    Studies over the last 8 years have identified 3 potential channels that appear to release ATP from Type II cells in response to taste stimuli. These studies have taken different methodological approaches but have all provided data supporting their candidate channel as the ATP release channel. These potential channels include Pannexin 1, Connexins (30 and/or 43), and most recently, the Calhm1 channel. Two papers in this issue of Chemical Senses provide compelling new evidence that Pannexin 1 is not the ATP release channel. Tordoff et al. did a thorough behavioral analysis of the Pannexin1 knock out mouse and found that these animals have the same behavioral responses as wild type mice for 7 different taste stimuli that were tested. Vandenbeuch et al. presented an equally thorough analysis of the gustatory nerve responses in the Pannexin1 knock out mouse and found no differences compared with controls. Thus when the role of Pannexin 1 is analyzed at the systems level, it is not required for normal taste perception. Further studies are needed to determine the role of this hemichannel in taste cells.

  7. Immunolocalization and expression of small-conductance calcium-activated potassium channels in human myometrium

    DEFF Research Database (Denmark)

    Rosenbaum, Sofia T; Svalø, Julie; Nielsen, Karsten;

    2012-01-01

    Small-conductance calcium-activated potassium (SK3) channels have been detected in human myometrium and we have previously shown a functional role of SK channels in human myometrium in vitro. The aims of this study were to identify the precise localization of SK3 channels and to quantify SK3 mRNA...

  8. New Role of P/Q-type Voltage-gated Calcium Channels

    DEFF Research Database (Denmark)

    Hansen, Pernille B L

    2015-01-01

    Voltage-gated calcium channels are important for the depolarization-evoked contraction of vascular smooth muscle cells (SMCs), with L-type channels being the classical channel involved in this mechanism. However, it has been demonstrated that the CaV2.1 subunit, which encodes a neuronal isoform o...

  9. The Need for a Rational Approach to Vasoconstrictive Syndromes: Transcranial Doppler and Calcium Channel Blockade in Reversible Cerebral Vasoconstriction Syndrome

    Directory of Open Access Journals (Sweden)

    Elisabeth B. Marsh

    2016-07-01

    Full Text Available Introduction: Reversible cerebral vasoconstriction syndrome (RCVS typically affects young patients and left untreated can result in hemorrhage or ischemic stroke. Though the disorder has been well characterized in the literature, the most appropriate way to diagnose, treat, and evaluate therapeutic response remains unclear. In previous studies, transcranial Doppler ultrasound (TCD has shown elevated velocities indicative of vasospasm. This imaging modality is noninvasive and inexpensive; an attractive option for diagnosis and therapeutic monitoring if it is sensitive enough to detect changes in the acute setting given that RCVS often affects the distal vessels early in the course of disease. There is also limited data that calcium channel blockade may be effective in treating vasospasm secondary to RCVS, though the agent of choice, formulation, and dose are unclear. Methods: We report a small cohort of seven patients presenting with thunderclap headache whose vascular imaging was consistent with RCVS. All were treated with calcium channel blockade and monitored with TCD performed every 1–2 days. Results: On presentation, TCD correlated with standard neuroimaging findings of vasospasm (on MR, CT, and conventional angiography. TCD was also able to detect improvement in velocities in the acute setting that correlated well with initiation of calcium channel blockade. Long-acting verapamil appeared to have the greatest effect on velocities compared to nimodipine and shorter-acting calcium channel blockers. Conclusion: Though small, our cohort demonstrates potential utility of TCD to monitor RCVS, and relative superiority of extended-release verapamil over other calcium channel blockers, illustrating the need for larger randomized trials.

  10. Signal processing by T-type calcium channel interactions in the cerebellum

    Directory of Open Access Journals (Sweden)

    Jordan D.T. Engbers

    2013-11-01

    Full Text Available T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs. In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (IT and hyperpolarization-activated cation current (IH are activated during trains of IPSPs. These currents have distinct, and yet synergistic, roles in the subthreshold domain with IT generating a rebound burst and IH controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing IH to increase the efficacy of IT, and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect effects on

  11. Signal processing by T-type calcium channel interactions in the cerebellum.

    Science.gov (United States)

    Engbers, Jordan D T; Anderson, Dustin; Zamponi, Gerald W; Turner, Ray W

    2013-11-27

    T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa) channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs). In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (I T) and hyperpolarization-activated cation current (I H) are activated during trains of inhibitory postsynaptic potentials. These currents have distinct, and yet synergistic, roles in the subthreshold domain with I T generating a rebound burst and I H controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing I H to increase the efficacy of I T and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect

  12. Signal processing by T-type calcium channel interactions in the cerebellum

    Science.gov (United States)

    Engbers, Jordan D. T.; Anderson, Dustin; Zamponi, Gerald W.; Turner, Ray W.

    2013-01-01

    T-type calcium channels of the Cav3 family are unique among voltage-gated calcium channels due to their low activation voltage, rapid inactivation, and small single channel conductance. These special properties allow Cav3 calcium channels to regulate neuronal processing in the subthreshold voltage range. Here, we review two different subthreshold ion channel interactions involving Cav3 channels and explore the ability of these interactions to expand the functional roles of Cav3 channels. In cerebellar Purkinje cells, Cav3 and intermediate conductance calcium-activated potassium (IKCa) channels form a novel complex which creates a low voltage-activated, transient outward current capable of suppressing temporal summation of excitatory postsynaptic potentials (EPSPs). In large diameter neurons of the deep cerebellar nuclei, Cav3-mediated calcium current (IT) and hyperpolarization-activated cation current (IH) are activated during trains of inhibitory postsynaptic potentials. These currents have distinct, and yet synergistic, roles in the subthreshold domain with IT generating a rebound burst and IH controlling first spike latency and rebound spike precision. However, by shortening the membrane time constant the membrane returns towards resting value at a faster rate, allowing IH to increase the efficacy of IT and increase the range of burst frequencies that can be generated. The net effect of Cav3 channels thus depends on the channels with which they are paired. When expressed in a complex with a KCa channel, Cav3 channels reduce excitability when processing excitatory inputs. If functionally coupled with an HCN channel, the depolarizing effect of Cav3 channels is accentuated, allowing for efficient inversion of inhibitory inputs to generate a rebound burst output. Therefore, signal processing relies not only on the activity of individual subtypes of channels but also on complex interactions between ion channels whether based on a physical complex or by indirect

  13. Microtubule-Dependent Mitochondria Alignment Regulates Calcium Release in Response to Nanomechanical Stimulus in Heart Myocytes

    Directory of Open Access Journals (Sweden)

    Michele Miragoli

    2016-01-01

    Full Text Available Arrhythmogenesis during heart failure is a major clinical problem. Regional electrical gradients produce arrhythmias, and cellular ionic transmembrane gradients are its originators. We investigated whether the nanoscale mechanosensitive properties of cardiomyocytes from failing hearts have a bearing upon the initiation of abnormal electrical activity. Hydrojets through a nanopipette indent specific locations on the sarcolemma and initiate intracellular calcium release in both healthy and heart failure cardiomyocytes, as well as in human failing cardiomyocytes. In healthy cells, calcium is locally confined, whereas in failing cardiomyocytes, calcium propagates. Heart failure progressively stiffens the membrane and displaces sub-sarcolemmal mitochondria. Colchicine in healthy cells mimics the failing condition by stiffening the cells, disrupting microtubules, shifting mitochondria, and causing calcium release. Uncoupling the mitochondrial proton gradient abolished calcium initiation in both failing and colchicine-treated cells. We propose the disruption of microtubule-dependent mitochondrial mechanosensor microdomains as a mechanism for abnormal calcium release in failing heart.

  14. Evaluation of pH, calcium ion release and antimicrobial activity of a new calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    Fernanda de Carvalho Panzeri Pires-de-Souza

    2013-07-01

    Full Text Available This study evaluated the pH, calcium ion release and antimicrobial activity of EndoBinder (EB, containing different radiopacifiers: bismuth oxide (Bi2O3, zinc oxide (ZnO or zirconium oxide (ZrO2, in comparison to MTA. For pH and calcium ion release tests, 5 specimens per group (n = 5 were immersed into 10 mL of distilled and deionized water at 37°C. After 2, 4, 12, 24, 48 h; 7, 14 and 28 days, the pH was measured and calcium ion release quantified in an atomic absorption spectrophotometer. For antimicrobial activity, the cements were tested against S. aureus, E. coli, E. faecalis and C. albicans, in triplicate. MTA presented higher values for pH and calcium ion release than the other groups, however, with no statistically significant difference after 28 days (p > 0.05; and the largest inhibition halos for all strains, with no significant difference (E. coli and E. faecalis for pure EB and EB + Bi2O3 (p > 0.05. EB presented similar performance to that of MTA as regards pH and calcium ion release; however, when ZnO and ZrO2 were used, EB did not present antimicrobial activity against some strains.

  15. Evolving therapeutic indications for N-type calcium channel blockers: from chronic pain to alcohol abuse.

    Science.gov (United States)

    Belardetti, Francesco

    2010-05-01

    Clinical exploitation of the therapeutic potential of calcium channels has long been limited to L-type blockers for cardiovascular diseases. Recently, N-type blockers have been fully validated for the treatment of chronic pain, following approval of the intrathecally active ziconotide (Prialt(®)). This review describes the successful efforts to broaden the therapeutic scope of this mechanism to other major CNS indications, based on the discovery of N-type blockers orally active against pain. In animal models, the N-type blocker and pain-reducing NP078585 is efficacious against key elements of ethanol dependency, including self-administration and relapse. NP078585 moderately stimulates brain dopamine release without inducing reward or hyperlocomotion. N-type blockers may emerge as a novel class of 'dopamine stabilizers' for the treatment of drug dependency and other neuropsychiatric disorders without the side effects of current therapies. PMID:21426203

  16. Kinetics of release of methylene blue immobilized in calcium alginate microparticles

    OpenAIRE

    Inal Bakhytkyzy; R. Ussenkyzy; D. Rahimbaeva

    2013-01-01

    The swelling kinetics of microparticles obtained with different concentrations of calcium chloride was studied to learn the ability of sodium alginate to gelation. To increase the effect of prolongation it is necessary to obtain microparticles with sustained release of drugs. For this purpose the drying kinetics of alginate microparticles was investigated. Also the kinetics of release of methylene blue immobilized in calcium alginate microparticles was studied. It was found that the release o...

  17. Preparation of TiO2 nanotubes/mesoporous calcium silicate composites with controllable drug release.

    Science.gov (United States)

    Xie, Chunling; Li, Ping; Liu, Yan; Luo, Fei; Xiao, Xiufeng

    2016-10-01

    Nanotube structures such as TiO2 nanotube (TNT) arrays produced by self-ordering electrochemical anodization have been extensively explored for drug delivery applications. In this study, we presented a new implantable drug delivery system that combined mesoporous calcium silicate coating with nanotube structures to achieve a controllable drug release of water soluble and antiphlogistic drug loxoprofen sodium. The results showed that the TiO2 nanotubes/mesoporous calcium silicate composites were successfully fabricated by a simple template method and the deposition of mesoporous calcium silicate increased with the soaking time. Moreover, the rate of deposition of biological mesoporous calcium silicate on amorphous TNTs was better than that on anatase TNTs. Further, zinc-incorporated mesoporous calcium silicate coating, produced by adding a certain concentration of zinc nitrate into the soaking system, displayed improved chemical stability. A significant improvement in the drug release characteristics with reduced burst release and sustained release was demonstrated. PMID:27287140

  18. Spontaneous and CRH-Induced Excitability and Calcium Signaling in Mice Corticotrophs Involves Sodium, Calcium, and Cation-Conducting Channels.

    Science.gov (United States)

    Zemkova, Hana; Tomić, Melanija; Kucka, Marek; Aguilera, Greti; Stojilkovic, Stanko S

    2016-04-01

    Transgenic mice expressing the tdimer2(12) form of Discosoma red fluorescent protein under control of the proopiomelanocortin gene's regulatory elements are a useful model for studying corticotrophs. Using these mice, we studied the ion channels and mechanisms controlling corticotroph excitability. Corticotrophs were either quiescent or electrically active, with a 22-mV difference in the resting membrane potential (RMP) between the 2 groups. In quiescent cells, CRH depolarized the membrane, leading to initial single spiking and sustained bursting; in active cells, CRH further facilitated or inhibited electrical activity and calcium spiking, depending on the initial activity pattern and CRH concentration. The stimulatory but not inhibitory action of CRH on electrical activity was mimicked by cAMP independently of the presence or absence of arachidonic acid. Removal of bath sodium silenced spiking and hyperpolarized the majority of cells; in contrast, the removal of bath calcium did not affect RMP but reduced CRH-induced depolarization, which abolished bursting electrical activity and decreased the spiking frequency but not the amplitude of single spikes. Corticotrophs with inhibited voltage-gated sodium channels fired calcium-dependent action potentials, whereas cells with inhibited L-type calcium channels fired sodium-dependent spikes; blockade of both channels abolished spiking without affecting the RMP. These results indicate that the background voltage-insensitive sodium conductance influences RMP, the CRH-depolarization current is driven by a cationic conductance, and the interplay between voltage-gated sodium and calcium channels plays a critical role in determining the status and pattern of electrical activity and calcium signaling.

  19. T-type voltage-gated calcium channels regulate the tone of mouse efferent arterioles

    DEFF Research Database (Denmark)

    Poulsen, Christian B; Al-Mashhadi, Rozh H; Cribbs, Leanne L;

    2011-01-01

    Voltage-gated calcium channels are important for the regulation of renal blood flow and the glomerular filtration rate. Excitation-contraction coupling in afferent arterioles is known to require activation of these channels and we studied their role in the regulation of cortical efferent arteriolar...... tone. We used microdissected perfused mouse efferent arterioles and found a transient vasoconstriction in response to depolarization with potassium; an effect abolished by removal of extracellular calcium. The T-type voltage-gated calcium channel antagonists mibefradil and nickel blocked this potassium....... Low concentrations of nickel, an agent that blocks Ca(v)3.2, had a similar effect. Thus, T-type voltage-gated calcium channels are functionally important for depolarization-induced vasoconstriction and subsequent dilatation in mouse cortical efferent arterioles.Kidney International advance online...

  20. Dopamine midbrain neurons in health and Parkinson's disease: emerging roles of voltage-gated calcium channels and ATP-sensitive potassium channels.

    Science.gov (United States)

    Dragicevic, E; Schiemann, J; Liss, B

    2015-01-22

    Dopamine (DA) releasing midbrain neurons are essential for multiple brain functions, such as voluntary movement, working memory, emotion and cognition. DA midbrain neurons within the substantia nigra (SN) and the ventral tegmental area (VTA) exhibit a variety of distinct axonal projections and cellular properties, and are differentially affected in diseases like schizophrenia, attention deficit hyperactivity disorder, and Parkinson's disease (PD). Apart from having diverse functions in health and disease states, DA midbrain neurons display distinct electrical activity patterns, crucial for DA release. These activity patterns are generated and modulated by specific sets of ion channels. Recently, two ion channels have been identified, not only contributing to these activity patterns and to functional properties of DA midbrain neurons, but also seem to render SN DA neurons particularly vulnerable to degeneration in PD and its animal models: L-type calcium channels (LTCCs) and ATP-sensitive potassium channels (K-ATPs). In this review, we focus on the emerging physiological and pathophysiological roles of these two ion channels (and their complex interplay with other ion channels), particularly in highly vulnerable SN DA neurons, as selective degeneration of these neurons causes the major motor symptoms of PD.

  1. Reduced levels of intracellular calcium releasing in spermatozoa from asthenozoospermic patients

    Directory of Open Access Journals (Sweden)

    García Juan F

    2009-02-01

    Full Text Available Abstract Background Asthenozoospermia is one of the most common findings present in infertile males characterized by reduced or absent sperm motility, but its aetiology remains unknown in most cases. In addition, calcium is one of the most important ions regulating sperm motility. In this study we have investigated the progesterone-evoked intracellular calcium signal in ejaculated spermatozoa from men with normospermia or asthenozoospermia. Methods Human ejaculates were obtained from healthy volunteers and asthenospermic men by masturbation after 4–5 days of abstinence. For determination of cytosolic free calcium concentration, spermatozoa were loaded with the fluorescent ratiometric calcium indicator Fura-2. Results Treatment of spermatozoa from normospermic men with 20 micromolar progesterone plus 1 micromolar thapsigargin in a calcium free medium induced a typical transient increase in cytosolic free calcium concentration due to calcium release from internal stores. Similar results were obtained when spermatozoa were stimulated with progesterone alone. Subsequent addition of calcium to the external medium evoked a sustained elevation in cytosolic free calcium concentration indicative of capacitative calcium entry. However, when progesterone plus thapsigargin were administered to spermatozoa from patients with asthenozoospermia, calcium signal and subsequent calcium entry was much smaller compared to normospermic patients. As expected, pretreatment of normospermic spermatozoa with both the anti-progesterone receptor c262 antibody and with progesterone receptor antagonist RU-38486 decreased the calcium release induced by progesterone. Treatment of spermatozoa with cytochalasin D or jasplakinolide decreased the calcium entry evoked by depletion of internal calcium stores in normospermic patients, whereas these treatments proved to be ineffective at modifying the calcium entry in patients with asthenozoospermia. Conclusion Our results suggest

  2. Molecular Interactions between Tarantula Toxins and Low-Voltage-Activated Calcium Channels

    OpenAIRE

    Autoosa Salari; Benjamin S. Vega; Milescu, Lorin S.; Mirela Milescu

    2016-01-01

    Few gating-modifier toxins have been reported to target low-voltage-activated (LVA) calcium channels, and the structural basis of toxin sensitivity remains incompletely understood. Studies of voltage-gated potassium (Kv) channels have identified the S3b–S4 “paddle motif,” which moves at the protein-lipid interface to drive channel opening, as the target for these amphipathic neurotoxins. Voltage-gated calcium (Cav) channels contain four homologous voltage sensor domains, suggesting multiple t...

  3. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential.

    Science.gov (United States)

    Zamponi, Gerald W; Striessnig, Joerg; Koschak, Alexandra; Dolphin, Annette C

    2015-10-01

    Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep

  4. Activation of L-type calcium channels is required for gap junction-mediated intercellular calcium signaling in osteoblastic cells

    Science.gov (United States)

    Jorgensen, Niklas Rye; Teilmann, Stefan Cuoni; Henriksen, Zanne; Civitelli, Roberto; Sorensen, Ole Helmer; Steinberg, Thomas H.

    2003-01-01

    The propagation of mechanically induced intercellular calcium waves (ICW) among osteoblastic cells occurs both by activation of P2Y (purinergic) receptors by extracellular nucleotides, resulting in "fast" ICW, and by gap junctional communication in cells that express connexin43 (Cx43), resulting in "slow" ICW. Human osteoblastic cells transmit intercellular calcium signals by both of these mechanisms. In the current studies we have examined the mechanism of slow gap junction-dependent ICW in osteoblastic cells. In ROS rat osteoblastic cells, gap junction-dependent ICW were inhibited by removal of extracellular calcium, plasma membrane depolarization by high extracellular potassium, and the L-type voltage-operated calcium channel inhibitor, nifedipine. In contrast, all these treatments enhanced the spread of P2 receptor-mediated ICW in UMR rat osteoblastic cells. Using UMR cells transfected to express Cx43 (UMR/Cx43) we confirmed that nifedipine sensitivity of ICW required Cx43 expression. In human osteoblastic cells, gap junction-dependent ICW also required activation of L-type calcium channels and influx of extracellular calcium.

  5. Ionic channels and hormone release from peptidergic nerve terminals.

    Science.gov (United States)

    Lemos, J R; Nordmann, J J

    1986-09-01

    Although there is considerable evidence that depolarization of nerve cell terminals leads to the entry of Ca2+ and to the secretion of neurohormones and neurotransmitters, the details of how ionic currents control the release of neuroactive substances from nerve terminals are unknown. The small size of most nerve terminals has precluded direct analysis of membrane ionic currents and their influence on secretion. We now report that it is possible, using patch-clamp techniques, to study stimulus--secretion coupling in isolated peptidergic nerve terminals. Sinus gland terminals from Cardisoma are easily isolated following collagenase treatment and appear morphologically and electrically very similar to non-dissociated nerve endings. We have observed two types of single-channel currents not previously described. The first ('f') channel is activated by intracellular Na+ and the second ('s') by intracellular Ca2+. Both show little selectivity between Na+ and K+. In symmetrical K+, these cation channels have mean conductances of 69 and 213 pS, respectively. Furthermore, at least three types of Ca2+ channels can be reconstituted from nerve terminal membranes prepared from sinus glands. Nerve terminals can also be isolated from the rat neural lobe. These neurosecretosomes release oxytocin and vasopressin, in response to membrane depolarization, only in the presence of external Ca2+. The depolarization of the nerve endings is associated with an increase in intracellular free Ca2+ concentration and this increase, measured using a fluorescent indicator, is abolished by Ca2+ channel blockers. Channels similar in their properties to the f and s channels also exist in rat neural lobe endings. Since these channels have not been found in other neurones or neuronal structures they may be unique to peptidergic nerve terminals.

  6. Evaluation of calcium ion release and change in pH on combining calcium hydroxide with different vehicles

    Directory of Open Access Journals (Sweden)

    Charu Grover

    2014-01-01

    Full Text Available Introduction: Intracanal medicaments have traditionally been used in endodontics to disinfect root canals between appointments. Calcium hydroxide is widely used as an intracanal medicament for disinfection and to promote periapical healing. It is stable for long periods, harmless to the body, and bactericidal in a limited area. The efficacy of calcium hydroxide as a disinfectant is dependent on the availability of the hydroxyl ions in the solution that depends on the vehicle in which the calcium hydroxide is carried. In general, three types of vehicles are used: Aqueous, viscous or oily. Some in vitro studies have shown that the type of vehicle has a direct relationship with the concentration and the velocity of ionic liberation as well as with the antibacterial action when the paste is carried into a contaminated area. Aim of the Study: To evaluate the calcium ion release and measure the change in pH of the environment that occurred when calcium hydroxide was combined with different vehicles (distilled water, propylene glycol, calcium hydroxide containing gutta-percha points and chitosan over different time periods. Materials and Methods: Forty single rooted mandibular first premolar teeth were decoronated for this study. Working length was established and the root canals were enlarged and irrigation accomplished with 2 ml of NaOCl solution after every file. The teeth were then randomly divided into four groups. The canals were then packed with different preparations of calcium hydroxide using the following vehicles-distilled water, propylene glycol, gutta-percha points and chitosan. Calcium ion release in different groups was analyzed using an ultraviolet spectrophotometer at 220 nm. The change in pH of was determined using a pH meter. Results were statistically evaluated using one-way ANOVA test. Result: For calcium ion release, Group 2 showed cumulative drug release of 81.97% at the end of 15 days, whereas Group 1, 3 and 4 showed a release

  7. T-type calcium channel expression in cultured human neuroblastoma cells

    Institute of Scientific and Technical Information of China (English)

    Xianjie Wen; Shiyuan Xu; Lingling Wang; Hua Liang; Chengxiang Yang; Hanbing Wang; Hongzhen Liu

    2011-01-01

    Human neuroblastoma cells (SH-SY5Y) have similar structures and functions as neural cells and have been frequently used for cell culture studies of neural cell functions. Previous studies have revealed Land N-type calcium channels in SH-SY5Y cells. However, the distribution of the low -voltage activated calcium channel (namely called T-type calcium channel, including Cav3.1, Cav3.2, and Cav3.3) in SH-SY5Y cells remains poorly understood. The present study detected mRNA and protein expression of the T-type calcium channel (Cav3.1, Cav3.2, and Cav3.3) in cultured SH-SY5Y cells using real-time polymerase chain reaction (PCR) and western blot analysis. Results revealed mRNA and protein expression from all three T-type calcium channel subtypes in SH-SY5Y cells. Moreover,Cav3.1 was the predominant T-type calcium channel subtype in SH-SY5Y cells.

  8. Hydrogen peroxide mediates oxidant-dependent stimulation of arterial smooth muscle L-type calcium channels.

    Science.gov (United States)

    Chaplin, Nathan L; Amberg, Gregory C

    2012-05-01

    Changes in calcium and redox homeostasis influence multiple cellular processes. Dysregulation of these signaling modalities is associated with pathology in cardiovascular, neuronal, endocrine, and other physiological systems. Calcium and oxidant signaling mechanisms are frequently inferred to be functionally related. To address and clarify this clinically relevant issue in the vasculature we tested the hypothesis that the ubiquitous reactive oxygen molecule hydrogen peroxide mediates oxidant-dependent stimulation of cerebral arterial smooth muscle L-type calcium channels. Using a combinatorial approach including intact arterial manipulations, electrophysiology, and total internal reflection fluorescence imaging, we found that application of physiological levels of hydrogen peroxide to isolated arterial smooth muscle cells increased localized calcium influx through L-type calcium channels. Similarly, oxidant-dependent stimulation of L-type calcium channels by the vasoconstrictor ANG II was abolished by intracellular application of catalase. Catalase also prevented ANG II from increasing localized subplasmalemmal sites of increased oxidation previously associated with colocalized calcium influx through L-type channels. Furthermore, catalase largely attenuated the contractile response of intact cerebral arterial segments to ANG II. In contrast, enhanced dismutation of superoxide to hydrogen peroxide with SOD had no effect on ANG II-dependent stimulation of L-type calcium channels. From these data we conclude that hydrogen peroxide is important for oxidant-dependent regulation of smooth muscle L-type calcium channels and arterial function. These data also support the emerging concept of hydrogen peroxide as a biologically relevant oxidant second messenger in multiple cell types with a diverse array of physiological functions.

  9. Multi-ion conduction bands in a simple model of calcium ion channels

    CERN Document Server

    Kaufman, I; Tindjong, R; McClintock, P V E; Eisenberg, R S

    2012-01-01

    We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. This structure comprises distinct regions of high conductance (conduction bands) M0, M1, M2 separated by regions of zero-conductance (stop-bands). Two of these conduction bands, M1 and M2, demonstrate high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels.

  10. A different dihydropyridine calcium channel blocker in hypertensive patients who developed pedal edema on dihydropyridine calcium channel blocker therapy

    Directory of Open Access Journals (Sweden)

    Ayşe Yüksel

    2014-03-01

    Full Text Available Abstract Aim. Dihydropyridine calcium channel blockers (CCB are widely preferred for the treatment of hypertension for their efficacy, metabolic neutrality and low side effect profile. However pedal edema formation limits their usage. The aim of the present study is to evaluate the incidence of pedal edema formation with a different dihydropyridine CCB in hypertensive patients who developed pedal edema during a dihydropyridine CCB therapy. Method. Fifty-eight hypertensive patients (34 female, 24 male, mean age: 65.3±10.5 in whom pedal edema developed during treatment with a dihydropyridine CCB (amlodipine 10mg/day in 40 patients, amlodipine 5mg/day in 14 patients, nifedipine GITS 30mg/day in 4 patients were enrolled. CCB which caused pedal edema was withdrawn and a different CCB (felodipine or lacidipine were initiated after the resolution of the pedal edema. CCB therapy was continued as long as the patient tolerated pedal edema. Results. At the end of one year, 44 out of 58 patients (36 [81.8%] free of pedal edema, 8 [19.2%] with pedal edema continued CCB therapy. Eleven (37.9% patients in the felodipine group and 9 (31.0% patients in the lacidipine group developed pedal edema. In 7 patients in felodipine group and in 5 patients in the lacidipine group the study drug was withdrawn due to pedal edema. In two patients, study drug was withdrawn due to intractable headache (felodipine group or due to flushing (lacidipine group. Conclusion. A different group of dihydropyridine CCB be used as an alternative therapy for hypertension whenever pedal edema develops during treatment with a dihydropyridine CCB.

  11. Calcium-activated potassium channels in insect pacemaker neurons as unexpected target site for the novel fumigant dimethyl disulfide.

    Science.gov (United States)

    Gautier, Hélène; Auger, Jacques; Legros, Christian; Lapied, Bruno

    2008-01-01

    Dimethyl disulfide (DMDS), a plant-derived insecticide, is a promising fumigant as a substitute for methyl bromide. To further understand the mode of action of DMDS, we examined its effect on cockroach octopaminergic neurosecretory cells, called dorsal unpaired median (DUM) neurons, using whole-cell patch-clamp technique, calcium imaging and antisense oligonucleotide strategy. At low concentration (1 microM), DMDS modified spontaneous regular spike discharge into clear bursting activity associated with a decrease of the amplitude of the afterhyperpolarization. This effect led us to suspect alterations of calcium-activated potassium currents (IKCa) and [Ca(2+)](i) changes. We showed that DMDS reduced amplitudes of both peak transient and sustained components of the total potassium current. IKCa was confirmed as a target of DMDS by using iberiotoxin, cadmium chloride, and pSlo antisense oligonucleotide. In addition, we showed that DMDS induced [Ca(2+)](i) rise in Fura-2-loaded DUM neurons. Using calcium-free solution, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxy-phenyl)ethyl]-acetamide (LOE 908) [an inhibitor of transient receptor potential (TRP)gamma], we demonstrated that TRPgamma initiated calcium influx. By contrast, omega-conotoxin GVIA (an inhibitor of N-type high-voltage-activated calcium channels), did not affect the DMDS-induced [Ca(2+)](i) rise. Finally, the participation of the calcium-induced calcium release mechanism was investigated using thapsigargin, caffeine, and ryanodine. Our study revealed that DMDS-induced elevation in [Ca(2+)](i) modulated IKCa in an unexpected bell-shaped manner via intracellular calcium. In conclusion, DMDS affects multiple targets, which could be an effective way to improve pest control efficacy of fumigation. PMID:17942746

  12. Multi-ion conduction bands in a simple model of calcium ion channels

    International Nuclear Information System (INIS)

    We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. With increasing Qf, there are distinct regions of high conductance (conduction bands) M0, M1, M2 separated by regions of almost zero-conductance (stop-bands). Two of these conduction bands, M1 and M2, are related to the saturated calcium occupancies of P = 1 and P = 2, respectively and demonstrate self-sustained conductivity. Despite the model's limitations, its M1 and M2 bands show high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels. The non-selective band M0 can be identified with a non-selective cation channel, or with OmpF porin. (paper)

  13. Inhibitory effect of calcium channel blockers on proliferation of human glioma cells in vitro

    International Nuclear Information System (INIS)

    The effects of 2 specific calcium channel blockers, verapamil and nimodipine, on the proliferation of human glioma tumour cells were investigated in vitro. Tumour tissues for primary cell cultures were obtained bioptically from 3 patients with the histopathological diagnosis of glioblastoma. The [3H]-thymidine incorporation into glioma tumour cells DNA was used as a sensitive index of the cell proliferation. It was found that varapamil (104-105M) and nimodipine (104-106M) significantly inhibited the [3H]-thymidine uptake in a dose-related manner. The inhibitory effect of both calcium channel antagonists was reversed by stimultancous addition of calcium chloride (5x103M). These results indicate that verapamil and nimodipine may exert an antiproliferative effect on glioma cells growth acting through a blokade of specific voltage-dependent calcium channels. (author)

  14. The genetic background affects the vascular response in T-type calcium channels 3.2 deficient mice

    DEFF Research Database (Denmark)

    Svenningsen, Per; Hansen, Pernille B L

    2016-01-01

    -type channels are the dominant Ca(2+) entry pathway in vascular smooth muscle cells, however, T-type calcium channels are also expressed in the cardiovascular system where they play a functional role in the regulation of both contraction and vasodilation in (Chen et al. 2003; Hansen et al. 2001). This article......Voltage-gated calcium channels (Cav ) are important regulators of vascular tone and are attractive targets for pharmacological treatment of hypertension. The clinical used calcium blockers are often not selective for one channel but affect several types of calcium channels (Hansen 2015). L...

  15. The TRPV5/6 calcium channels contain multiple calmodulin binding sites with differential binding properties.

    NARCIS (Netherlands)

    Kovalevskaya, N.V.; Bokhovchuk, F.M.; Vuister, G.W.

    2012-01-01

    The epithelial Ca(2+) channels TRPV5/6 (transient receptor potential vanilloid 5/6) are thoroughly regulated in order to fine-tune the amount of Ca(2+) reabsorption. Calmodulin has been shown to be involved into calcium-dependent inactivation of TRPV5/6 channels by binding directly to the distal C-t

  16. A Calcium-Dependent Protein Kinase Interactswith and Activates A Calcium Channel toRequlate Pollen Tube Growth

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    ABSTRACT Calcium, as a ubiquitous second messenger, plays essential roles in tip-growing cells, such as animal neu-rons, plant pollen tubes, and root hairs. However, little is known concerning the regulatory mechanisms that code anddecode Ca2+ signals in plants. The evidence presented here indicates that a calcium-dependent protein kinase, CPK32,controls polar growth of pollen tubes. Overexpression of CPK32 disrupted the polar growth along with excessive Ca2+accumulation in the tip. A search of downstream effector molecules for CPK32 led to identification of a cyclic nucleotide-gated channel, CNGC18, as an interacting partner for CPK32. Co-expression of CPK32 and CNGC18 resulted in activationof CNGC18 in Xenopus oocytes where expression of CNGC18 alone did not exhibit significant calcium channel activity.Overexpression of CNGC18 produced a growth arrest phenotype coupled with accumulation of calcium in the tip, simi-lar to that induced by CPK32 overexpression. Co-expression of CPK32 and CNGC18 had a synergistic effect leading tomore severe depolarization of pollen tube growth. These results provide a potential feed-forward mechanism in whichcalcium-activated CPK32 activates CNGC18, further promoting calcium entry during the elevation phase of Ca2+ oscilla-tions in the polar growth of pollen tubes.

  17. Voltage-dependent calcium channels in skeletal muscle transverse tubules. Measurements of calcium efflux in membrane vesicles

    International Nuclear Information System (INIS)

    Transverse tubule membranes isolated from rabbit skeletal muscle consist mainly of sealed vesicles that are oriented primarily inside out. These membranes contain a high density of binding sites for 1,4-dihydropyridine calcium channel antagonists. The presence of functional voltage-dependent calcium channels in these membranes has been demonstrated by their ability to mediate 45Ca2+ efflux in response to changes in membrane potential. Fluorescence changes of the voltage-sensitive dye, 3,3'-dipropyl-2,2'-thiadicarbocyanine, have shown that transverse tubule vesicles may generate and maintain membrane potentials in response to establishing potassium gradients across the membrane in the presence of valinomycin. A two-step procedure has been developed to measure voltage-dependent calcium fluxes. Vesicles loaded with 45Ca2+ are first diluted into a buffer designed to generate a membrane potential mimicking the resting state of the cell and to reduce the extravesicular Ca2+ to sub-micromolar levels. 45Ca2+ efflux is then measured upon subsequent depolarization. Flux responses are modulated with appropriate pharmacological specificity by 1,4-dihydropyridines and are inhibited by other calcium channel antagonists such as lanthanum and verapamil

  18. Calcium influx through L-type channels attenuates skeletal muscle contraction via inhibition of adenylyl cyclases.

    Science.gov (United States)

    Menezes-Rodrigues, Francisco Sandro; Pires-Oliveira, Marcelo; Duarte, Thiago; Paredes-Gamero, Edgar Julian; Chiavegatti, Tiago; Godinho, Rosely Oliveira

    2013-11-15

    Skeletal muscle contraction is triggered by acetylcholine induced release of Ca(2+) from sarcoplasmic reticulum. Although this signaling pathway is independent of extracellular Ca(2+), L-type voltage-gated calcium channel (Cav) blockers have inotropic effects on frog skeletal muscles which occur by an unknown mechanism. Taking into account that skeletal muscle fiber expresses Ca(+2)-sensitive adenylyl cyclase (AC) isoforms and that cAMP is able to increase skeletal muscle contraction force, we investigated the role of Ca(2+) influx on mouse skeletal muscle contraction and the putative crosstalk between extracellular Ca(2+) and intracellular cAMP signaling pathways. The effects of Cav blockers (verapamil and nifedipine) and extracellular Ca(2+) chelator EGTA were evaluated on isometric contractility of mouse diaphragm muscle under direct electrical stimulus (supramaximal voltage, 2 ms, 0.1 Hz). Production of cAMP was evaluated by radiometric assay while Ca(2+) transients were assessed by confocal microscopy using L6 cells loaded with fluo-4/AM. Ca(2+) channel blockers verapamil and nifedipine had positive inotropic effect, which was mimicked by removal of extracellular Ca(+2) with EGTA or Ca(2+)-free Tyrode. While phosphodiesterase inhibitor IBMX potentiates verapamil positive inotropic effect, it was abolished by AC inhibitors SQ22536 and NYK80. Finally, the inotropic effect of verapamil was associated with increased intracellular cAMP content and mobilization of intracellular Ca(2+), indicating that positive inotropic effects of Ca(2+) blockers depend on cAMP formation. Together, our results show that extracellular Ca(2+) modulates skeletal muscle contraction, through inhibition of Ca(2+)-sensitive AC. The cross-talk between extracellular calcium and cAMP-dependent signaling pathways appears to regulate the extent of skeletal muscle contraction responses.

  19. Discovery of novel tetrahydroisoquinoline derivatives as orally active N-type calcium channel blockers with high selectivity for hERG potassium channels.

    Science.gov (United States)

    Ogiyama, Takashi; Inoue, Makoto; Honda, Shugo; Yamada, Hiroyoshi; Watanabe, Toshihiro; Gotoh, Takayasu; Kiso, Tetsuo; Koakutsu, Akiko; Kakimoto, Shuichiro; Shishikura, Jun-ichi

    2014-12-15

    N-type calcium channels represent a promising target for the treatment of neuropathic pain. The selective N-type calcium channel blocker ziconotide ameliorates severe chronic pain but has a narrow therapeutic window and requires intrathecal administration. We identified tetrahydroisoquinoline derivative 1a as a novel potent N-type calcium channel blocker. However, this compound also exhibited potent inhibitory activity against hERG channels. Structural optimizations led to identification of (1S)-(1-cyclohexyl-3,4-dihydroisoquinolin-2(1H)-yl)-2-{[(1-hydroxycyclohexyl)methyl]amino}ethanone ((S)-1h), which exhibited high selectivity for hERG channels while retaining potency for N-type calcium channel inhibition. (S)-1h went on to demonstrate in vivo efficacy as an orally available N-type calcium channel blocker in a rat spinal nerve ligation model of neuropathic pain. PMID:25456079

  20. Calcium influx through CRAC channels controls actin organization and dynamics at the immune synapse.

    Science.gov (United States)

    Hartzell, Catherine A; Jankowska, Katarzyna I; Burkhardt, Janis K; Lewis, Richard S

    2016-01-01

    T cell receptor (TCR) engagement opens Ca(2+) release-activated Ca(2+) (CRAC) channels and triggers formation of an immune synapse between T cells and antigen-presenting cells. At the synapse, actin reorganizes into a concentric lamellipod and lamella with retrograde actin flow that helps regulate the intensity and duration of TCR signaling. We find that Ca(2+) influx is required to drive actin organization and dynamics at the synapse. Calcium acts by promoting actin depolymerization and localizing actin polymerization and the actin nucleation promotion factor WAVE2 to the periphery of the lamellipod while suppressing polymerization elsewhere. Ca(2+)-dependent retrograde actin flow corrals ER tubule extensions and STIM1/Orai1 complexes to the synapse center, creating a self-organizing process for CRAC channel localization. Our results demonstrate a new role for Ca(2+) as a critical regulator of actin organization and dynamics at the synapse, and reveal potential feedback loops through which Ca(2+) influx may modulate TCR signaling. PMID:27440222

  1. Calcium influx through CRAC channels controls actin organization and dynamics at the immune synapse

    Science.gov (United States)

    Hartzell, Catherine A; Jankowska, Katarzyna I; Burkhardt, Janis K; Lewis, Richard S

    2016-01-01

    T cell receptor (TCR) engagement opens Ca2+ release-activated Ca2+ (CRAC) channels and triggers formation of an immune synapse between T cells and antigen-presenting cells. At the synapse, actin reorganizes into a concentric lamellipod and lamella with retrograde actin flow that helps regulate the intensity and duration of TCR signaling. We find that Ca2+ influx is required to drive actin organization and dynamics at the synapse. Calcium acts by promoting actin depolymerization and localizing actin polymerization and the actin nucleation promotion factor WAVE2 to the periphery of the lamellipod while suppressing polymerization elsewhere. Ca2+-dependent retrograde actin flow corrals ER tubule extensions and STIM1/Orai1 complexes to the synapse center, creating a self-organizing process for CRAC channel localization. Our results demonstrate a new role for Ca2+ as a critical regulator of actin organization and dynamics at the synapse, and reveal potential feedback loops through which Ca2+ influx may modulate TCR signaling. DOI: http://dx.doi.org/10.7554/eLife.14850.001 PMID:27440222

  2. BARP suppresses voltage-gated calcium channel activity and Ca2+-evoked exocytosis.

    Science.gov (United States)

    Béguin, Pascal; Nagashima, Kazuaki; Mahalakshmi, Ramasubbu N; Vigot, Réjan; Matsunaga, Atsuko; Miki, Takafumi; Ng, Mei Yong; Ng, Yu Jin Alvin; Lim, Chiaw Hwee; Tay, Hock Soon; Hwang, Le-Ann; Firsov, Dmitri; Tang, Bor Luen; Inagaki, Nobuya; Mori, Yasuo; Seino, Susumu; Launey, Thomas; Hunziker, Walter

    2014-04-28

    Voltage-gated calcium channels (VGCCs) are key regulators of cell signaling and Ca(2+)-dependent release of neurotransmitters and hormones. Understanding the mechanisms that inactivate VGCCs to prevent intracellular Ca(2+) overload and govern their specific subcellular localization is of critical importance. We report the identification and functional characterization of VGCC β-anchoring and -regulatory protein (BARP), a previously uncharacterized integral membrane glycoprotein expressed in neuroendocrine cells and neurons. BARP interacts via two cytosolic domains (I and II) with all Cavβ subunit isoforms, affecting their subcellular localization and suppressing VGCC activity. Domain I interacts at the α1 interaction domain-binding pocket in Cavβ and interferes with the association between Cavβ and Cavα1. In the absence of domain I binding, BARP can form a ternary complex with Cavα1 and Cavβ via domain II. BARP does not affect cell surface expression of Cavα1 but inhibits Ca(2+) channel activity at the plasma membrane, resulting in the inhibition of Ca(2+)-evoked exocytosis. Thus, BARP can modulate the localization of Cavβ and its association with the Cavα1 subunit to negatively regulate VGCC activity.

  3. Do Ca2+-adsorbing ceramics reduce the release of calcium ions from gypsum-based biomaterials?

    Science.gov (United States)

    Belcarz, Anna; Zalewska, Justyna; Pałka, Krzysztof; Hajnos, Mieczysław; Ginalska, Grazyna

    2015-02-01

    Bone implantable materials based on calcium sulfate dihydrate dissolve quickly in tissue liquids and release calcium ions at very high levels. This phenomenon induces temporary toxicity for osteoblasts, may cause local inflammation and delay the healing process. Reduction in the calcium ion release rate by gypsum could be therefore beneficial for the healing of gypsum-filled bone defects. The aim of this study concerned the potential use of calcium phosphate ceramics of various porosities for the reduction of high Ca(2+) ion release from gypsum-based materials. Highly porous ceramics failed to reduce the level of Ca(2+) ions released to the medium in a continuous flow system. However, it succeeded to shorten the period of high calcium level. It was not the phase composition but the high porosity of ceramics that was found crucial for both the shortening of the Ca(2+) release-related toxicity period and intensification of apatite deposition on the composite. Nonporous ceramics was completely ineffective for this purpose and did not show any ability to absorb calcium ions at a significant level. Moreover, according to our observations, complex studies imitating in vivo systems, rather than standard tests, are essential for the proper evaluation of implantable biomaterials. PMID:25492196

  4. Somatic ATP release from guinea pig sympathetic neurons does not require calcium-induced calcium release from internal stores

    OpenAIRE

    Merriam, Laura A.; Locknar, Sarah A.; Girard, Beatrice M.; Parsons, Rodney L.

    2010-01-01

    Prior studies indicated that a Ca2+-dependent release of ATP can be initiated from the soma of sympathetic neurons dissociated from guinea pig stellate ganglia. Previous studies also indicated that Ca2+-induced Ca2+ release (CICR) can modulate membrane excitability in these same neurons. As Ca2+ release from internal stores is thought to support somatodendritic transmitter release in other neurons, the present study investigated whether CICR is essential for somatic ATP release from dissociat...

  5. Effect of dendroaspis natriuretic peptide (DNP) on L-type calcium channel current and its pathway.

    Science.gov (United States)

    Zhang, Shu-Ying; Cai, Zheng-Xu; Li, Ping; Cai, Chun-Yu; Qu, Cheng-Long; Guo, Hui-Shu

    2010-09-24

    Dendroaspis natriuretic peptide (DNP), a newly-described natriuretic peptide, relaxes gastrointestinal smooth muscle. L-type calcium channel currents play an important role in regulating smooth muscle contraction. The effect of DNP on L-type calcium channel currents in gastrointestinal tract is still unclear. This study was designed to investigate the effect of DNP on barium current (I(Ba)) through the L-type calcium channel in gastric antral myocytes of guinea pigs and cGMP-pathway mechanism. The whole-cell patch-clamp technique was used to record L-type calcium channel currents. The content of cGMP in guinea pig gastric antral smooth muscle and perfusion solution was measured using radioimmunoassay. DNP markedly enhanced cGMP levels in gastric antral smooth muscle tissue and in perfusion medium. DNP concentration-dependently inhibited I(Ba) in freshly isolated guinea pig gastric antral circular smooth muscle cells (SMCs) of guinea pigs. DNP-induced inhibition of I(Ba) was partially blocked by LY83583, an inhibitor of guanylate cyclase. KT5823, a cGMP-dependent protein kinase (PKG) inhibitor, almost completely blocked DNP-induced inhibition of I(Ba). However, DNP-induced inhibition of I(Ba) was potentiated by zaprinast, an inhibitor of cGMP-sensitive phosphodiesterase. Taken together, DNP inhibits L-type calcium channel currents via pGC-cGMP-PKG-dependent signal pathway in gastric antral myocytes of guinea pigs. PMID:20594955

  6. A ROS-Assisted Calcium Wave Dependent on the AtRBOHD NADPH Oxidase and TPC1 Cation Channel Propagates the Systemic Response to Salt Stress.

    Science.gov (United States)

    Evans, Matthew J; Choi, Won-Gyu; Gilroy, Simon; Morris, Richard J

    2016-07-01

    Plants exhibit rapid, systemic signaling systems that allow them to coordinate physiological and developmental responses throughout the plant body, even to highly localized and quickly changing environmental stresses. The propagation of these signals is thought to include processes ranging from electrical and hydraulic networks to waves of reactive oxygen species (ROS) and cytoplasmic Ca(2+) traveling throughout the plant. For the Ca(2+) wave system, the involvement of the vacuolar ion channel TWO PORE CHANNEL1 (TPC1) has been reported. However, the precise role of this channel and the mechanism of cell-to-cell propagation of the wave have remained largely undefined. Here, we use the fire-diffuse-fire model to analyze the behavior of a Ca(2+) wave originating from Ca(2+) release involving the TPC1 channel in Arabidopsis (Arabidopsis thaliana). We conclude that a Ca(2+) diffusion-dominated calcium-induced calcium-release mechanism is insufficient to explain the observed wave transmission speeds. The addition of a ROS-triggered element, however, is able to quantitatively reproduce the observed transmission characteristics. The treatment of roots with the ROS scavenger ascorbate and the NADPH oxidase inhibitor diphenyliodonium and analysis of Ca(2+) wave propagation in the Arabidopsis respiratory burst oxidase homolog D (AtrbohD) knockout background all led to reductions in Ca(2+) wave transmission speeds consistent with this model. Furthermore, imaging of extracellular ROS production revealed a systemic spread of ROS release that is dependent on both AtRBOHD and TPC1 These results suggest that, in the root, plant systemic signaling is supported by a ROS-assisted calcium-induced calcium-release mechanism intimately involving ROS production by AtRBOHD and Ca(2+) release dependent on the vacuolar channel TPC1. PMID:27261066

  7. A ROS-Assisted Calcium Wave Dependent on the AtRBOHD NADPH Oxidase and TPC1 Cation Channel Propagates the Systemic Response to Salt Stress1[OPEN

    Science.gov (United States)

    Evans, Matthew J.; Choi, Won-Gyu

    2016-01-01

    Plants exhibit rapid, systemic signaling systems that allow them to coordinate physiological and developmental responses throughout the plant body, even to highly localized and quickly changing environmental stresses. The propagation of these signals is thought to include processes ranging from electrical and hydraulic networks to waves of reactive oxygen species (ROS) and cytoplasmic Ca2+ traveling throughout the plant. For the Ca2+ wave system, the involvement of the vacuolar ion channel TWO PORE CHANNEL1 (TPC1) has been reported. However, the precise role of this channel and the mechanism of cell-to-cell propagation of the wave have remained largely undefined. Here, we use the fire-diffuse-fire model to analyze the behavior of a Ca2+ wave originating from Ca2+ release involving the TPC1 channel in Arabidopsis (Arabidopsis thaliana). We conclude that a Ca2+ diffusion-dominated calcium-induced calcium-release mechanism is insufficient to explain the observed wave transmission speeds. The addition of a ROS-triggered element, however, is able to quantitatively reproduce the observed transmission characteristics. The treatment of roots with the ROS scavenger ascorbate and the NADPH oxidase inhibitor diphenyliodonium and analysis of Ca2+ wave propagation in the Arabidopsis respiratory burst oxidase homolog D (AtrbohD) knockout background all led to reductions in Ca2+ wave transmission speeds consistent with this model. Furthermore, imaging of extracellular ROS production revealed a systemic spread of ROS release that is dependent on both AtRBOHD and TPC1. These results suggest that, in the root, plant systemic signaling is supported by a ROS-assisted calcium-induced calcium-release mechanism intimately involving ROS production by AtRBOHD and Ca2+ release dependent on the vacuolar channel TPC1. PMID:27261066

  8. Channel-Mediated Lactate Release by K+-Stimulated Astrocytes

    KAUST Repository

    Sotelo-Hitschfeld, T.

    2015-03-11

    Excitatory synaptic transmission is accompanied by a local surge in interstitial lactate that occurs despite adequate oxygen availability, a puzzling phenomenon termed aerobic glycolysis. In addition to its role as an energy substrate, recent studies have shown that lactate modulates neuronal excitability acting through various targets, including NMDA receptors and G-protein-coupled receptors specific for lactate, but little is known about the cellular and molecular mechanisms responsible for the increase in interstitial lactate. Using a panel of genetically encoded fluorescence nanosensors for energy metabolites, we show here that mouse astrocytes in culture, in cortical slices, and in vivo maintain a steady-state reservoir of lactate. The reservoir was released to the extracellular space immediately after exposure of astrocytes to a physiological rise in extracellular K+ or cell depolarization. Cell-attached patch-clamp analysis of cultured astrocytes revealed a 37 pS lactate-permeable ion channel activated by cell depolarization. The channel was modulated by lactate itself, resulting in a positive feedback loop for lactate release. A rapid fall in intracellular lactate levels was also observed in cortical astrocytes of anesthetized mice in response to local field stimulation. The existence of an astrocytic lactate reservoir and its quick mobilization via an ion channel in response to a neuronal cue provides fresh support to lactate roles in neuronal fueling and in gliotransmission.

  9. The role of voltage-gated calcium channels in neurotransmitter phenotype specification: Coexpression and functional analysis in Xenopus laevis

    OpenAIRE

    Lewis, Brittany B.; Miller, Lauren E.; Herbst, Wendy A; Saha, Margaret S.

    2014-01-01

    Calcium activity has been implicated in many neurodevelopmental events, including the specification of neurotransmitter phenotypes. Higher levels of calcium activity lead to an increased number of inhibitory neural phenotypes, whereas lower levels of calcium activity lead to excitatory neural phenotypes. Voltage-gated calcium channels (VGCCs) allow for rapid calcium entry and are expressed during early neural stages, making them likely regulators of activity-dependent neurotransmitter phenoty...

  10. Calcium-Activated Potassium Channels in Ischemia Reperfusion: A Brief Update

    Directory of Open Access Journals (Sweden)

    Jean-Yves eTano

    2014-10-01

    Full Text Available Ischemia and reperfusion (IR injury constitutes one of the major causes of cardiovascular morbidity and mortality. The discovery of new therapies to block/mediate the effects of IR is therefore an important goal in the biomedical sciences. Dysfunction associated with IR involves modification of calcium-activated potassium channels (KCa through different mechanisms, which are still under study. Respectively, the KCa family, major contributors to plasma membrane calcium influx in cells and essential players in the regulation of the vascular tone are interesting candidates. This family is divided into two groups including the large conductance (BKCa and the small/intermediate conductance (SKCa/IKCa K+ channels. In the heart and brain, these channels have been described to offer protection against IR injury. BKCa and SKCa channels deserve special attention since new data demonstrate that these channels are also expressed in mitochondria. More studies are however needed to fully determine their potential use as therapeutic targets.

  11. Calcium channel activity of purified human synexin and structure of the human synexin gene

    International Nuclear Information System (INIS)

    Synexin is a calcium-dependent membrane binding protein that not only fuses membranes but also acts as a voltage-dependent calcium channel. The authors have isolated and sequenced a set of overlapping cDNA clones for human synexin. The derived amino acid sequence of synexin reveals strong homology in the C-terminal domain with a previously identified class of calcium-dependent membrane binding proteins. These include endonexin II, lipocortin I, calpactin I heavy chain (p36), protein II, and calelectrin 67K. The Mr 51,000 synexin molecule can be divided into a unique, highly hydrophobic N-terminal domain of 167 amino acids and a conserved C-terminal region of 299 amino acids. The latter domain is composed of alternating hydrophobic and hydrophilic segments. Analysis of the entire structure reveals possible insights into such diverse properties as voltage-sensitive calcium channel activity, ion selectivity, affinity for phospholipids, and membrane fusion

  12. The mechanosensory calcium-selective ion channel: key component of a plasmalemmal control centre?

    Science.gov (United States)

    Pickard, B. G.; Ding, J. P.

    1993-01-01

    Mechanosensory calcium-selective ion channels probably serve to detect not only mechanical stress but also electrical, thermal, and diverse chemical stimuli. Because all stimuli result in a common output, most notably a shift in second messenger calcium concentration, the channels are presumed to serve as signal integrators. Further, insofar as second messenger calcium in turn gives rise to mechanical, electrical, and diverse chemical changes, the channels are postulated to initiate regulatory feedbacks. It is proposed that the channels and the feedback loops play a wide range of roles in regulating normal plant function, as well as in mediating disturbance of normal function by environmental stressors and various pathogens. In developing evidence for the physiological performance of the channel, a model for a cluster of regulatory plasmalemmal proteins and cytoskeletal elements grouped around a set of wall-to-membrane and transmembrane linkers has proved useful. An illustration of how the model might operate is presented. It is founded on the demonstration that several xenobiotics interfere both with normal channel behaviour and with gravitropic reception. Accordingly, the first part of the illustration deals with how the channels and the control system within which they putatively operate might initiate gravitropism. Assuming that gravitropism is an asymmetric expression of growth, the activities of the channels and the plasmalemmal control system are extrapolated to account for regulation of both rate and allometry of cell expansion. Finally, it is discussed how light, hormones, redox agents and herbicides could in principle affect growth via the putative plasmalemmal control cluster or centre.

  13. The Timothy syndrome mutation differentially affects voltage- and calcium-dependent inactivation of CaV1.2 L-type calcium channels

    OpenAIRE

    Barrett, Curtis F.; Tsien, Richard W.

    2008-01-01

    Calcium entry into excitable cells is an important physiological signal, supported by and highly sensitive to the activity of voltage-gated Ca2+ channels. After membrane depolarization, Ca2+ channels first open but then undergo various forms of negative feedback regulation including voltage- and calcium-dependent inactivation (VDI and CDI, respectively). Inactivation of Ca2+ channel activity is perturbed in a rare yet devastating disorder known as Timothy syndrome (TS), whose features include...

  14. Calcium-activated chloride channels in the apical region of mouse vomeronasal sensory neurons

    OpenAIRE

    Dibattista, Michele; Amjad, Asma; Maurya, Devendra Kumar; Sagheddu, Claudia; Montani, Giorgia; Tirindelli, Roberto; Menini, Anna

    2012-01-01

    The rodent vomeronasal organ plays a crucial role in several social behaviors. Detection of pheromones or other emitted signaling molecules occurs in the dendritic microvilli of vomeronasal sensory neurons, where the binding of molecules to vomeronasal receptors leads to the influx of sodium and calcium ions mainly through the transient receptor potential canonical 2 (TRPC2) channel. To investigate the physiological role played by the increase in intracellular calcium concentration in the api...

  15. A novel series of pyrazolylpiperidine N-type calcium channel blockers.

    Science.gov (United States)

    Subasinghe, Nalin L; Wall, Mark J; Winters, Michael P; Qin, Ning; Lubin, Mary Lou; Finley, Michael F A; Brandt, Michael R; Neeper, Michael P; Schneider, Craig R; Colburn, Raymond W; Flores, Christopher M; Sui, Zhihua

    2012-06-15

    Selective blockers of the N-type calcium channel have proven to be effective in animal models of chronic pain. However, even though intrathecally delivered synthetic ω-conotoxin MVIIA from Conus magnus (ziconotide [Prialt®]) has been approved for the treatment of chronic pain in humans, its mode of delivery and narrow therapeutic window have limited its usefulness. Therefore, the identification of orally active, small-molecule N-type calcium channel blockers would represent a significant advancement in the treatment of chronic pain. A novel series of pyrazole-based N-type calcium channel blockers was identified by structural modification of a high-throughput screening hit and further optimized to improve potency and metabolic stability. In vivo efficacy in rat models of inflammatory and neuropathic pain was demonstrated by a representative compound from this series. PMID:22608964

  16. Interactions of cryptosin with mammalian cardiac dihydropyridine-specific calcium channels

    International Nuclear Information System (INIS)

    Cryptosin, a new cardenolide, was found to be a potent inhibitor of cardiac Na+ and K+ dependent Adenosinetri-phosphatase. In experiments with dog heart ex vivo, development of inotropic and toxic effect correlated with changes in the cardiac dihydropyridine-specific calcium channels as measured by the binding of 3[H]PN 200-110. A significant change in the PN 200-110 binding was observed when guinea pig and dog heart sarcolemmal membranes were pre-incubated with cryptosin in vitro. Binding analysis of 3[H]PN 200-110 (Isradipine), a 1,4-dihydropyridine analog with very specific calcium channel binding properties, in both in vitro and ex vivo studies were consistent and indicated a non-specific type of interaction of cryptosin with mammalian cardiac 1,4-dihydropyridine-specific calcium channels

  17. A highly calcium-selective cation current activated by intracellular calcium release in MDCK cells.

    Science.gov (United States)

    Delles, C; Haller, T; Dietl, P

    1995-08-01

    1. The whole-cell patch clamp technique and fluorescence microscopy with the Ca2+ indicators fura-2 and fluo-3 were used to measure the whole-cell current and the free intracellular Ca2+ concentration ([Ca2+]i) in Madin-Darby canine kidney (MDCK) cells. 2. In a Ca(2+)-free bath solution, thapsigargin (TG) caused a transient increase of [Ca2+]i. Subsequent addition of Ca2+ caused a long lasting elevation of [Ca2+]i. 3. In a Ca(2+)-free bath solution, extracellular application of TG, ATP or ionomycin, or intracellular application of inositol 1,4,5-trisphosphate (IP3), caused a small but significant inward current (Iin) and a transient outward Ca(2+)-dependent K+ current (IK(Ca)), consistent with intracellular Ca2+ release. Subsequent addition of Ca2+ induced a prominent Iin with a current density of -4.2 +/- 0.7 pA pF-1. This Iin was unaffected by inositol 1,3,4,5-tetrakisphosphate (IP4). 4. Na+ replacement by mannitol, N-methyl-D-glucamine+ (NMG+), aminomethylidin-trimethanol+ (Tris+) or choline+ reduced Iin by 54, 65, 52 and 56%, respectively. This indicates an apparent Ca2+ selectivity over Na+ of 26:1. Iin was, however, unaffected by replacing Cl- with gluconate- or by the K+ channel blocker charybdotoxin (CTX). 5. Iin was completely blocked by La3+ (IC50 = 0.77 microM). Consistently, La3+ completely reversed the TG-induced elevation of [Ca2+]i. SK&F 96365 (1-[3-(4-methoxyphenyl)-propoxyl]-1-(4-methoxy-phenyl)-ethyl-1H-im idazole) HCl did not inhibit the TG-induced Iin. It did, however, exhibit a biphasic effect on [Ca2+]i, consisting of an initial Ca2+ decay and a subsequent Ca2+ elevation. La3+ completely reversed the SK&F 96365-induced elevation of [Ca2+]i. 6. In the absence of Na+, Iin was dependent on the bath Ca2+ concentration (EC50 = 1.02 mM). Ca2+ replacement by Ba2+ or Mn2+ resulted in a reduction of Iin by 95 and 94%, respectively. 7. From these experiments we conclude that Ca2+ release from intracellular Ca2+ stores, induced by different independent

  18. Inhibition of anaphylactic histamine release from heterologously sensitized mast cells: differential effects of drugs which interfere with calcium influx.

    Directory of Open Access Journals (Sweden)

    Kurose,Masao

    1981-11-01

    Full Text Available Drug effects were studied on anaphylactic histamine release from rat mast cells sensitized in vitro with mouse IgE antibody. When histamine release was elicited by adding Ca-++ at various times after antigen-stimulation of sensitized cells in Ca++-free medium, the drugs to be tested were added shortly before each Ca++ addition. Quercetin was effective only when added before or immediately after antigen. Theophylline and disodium cromoglycate (DSCG were active irrespective of the time interval between antigen and Ca++ addition. Verapamil was more effective when added before or simultaneously with antigen than when added later. When tested in the two-stage experiments, quercetin showed inhibition only in Stage 1 and verapamil was inhibitive primarily in Stage 1, while theophylline and DSCG wee only inhibitive in Stage 2. It seems that quercetin selectively and verapamil primarily act to block calcium-gate opening resulting from antigen-antibody interaction on the mast cell membrane, while theophylline and DSCG selectively inhibit the passage of calcium through open calcium channels.

  19. Modulation of mechanosensitive calcium-selective cation channels by temperature

    Science.gov (United States)

    Ding, J. P.; Pickard, B. G.

    1993-01-01

    Gating of associations of mechanosensitive Ca(2+)-selective cation co-channels in the plasmalemma of onion epidermis has a strong and unusual temperature dependence. Tension-dependent activity rises steeply as temperature is lowered from 25 degrees C to about 6 degrees C, but drops to a low level at about 5 degrees C. Under the conditions tested (with Mg2+ and K+ at the cytosolic face of outside-out membrane patches), promotion results both from more bursting at all observed linkage levels and from longer duration of bursts of co-channels linked as quadruplets and quintuplets. Co-channel conductance decreases linearly, but only modestly, with declining temperature. It is proposed that these and related mechanosensitive channels may participate in a variety of responses to temperature, including thermonasty, thermotropism, hydrotropism, and both cold damage and cold acclimation.

  20. Disruption of learned timing in P/Q calcium channel mutants.

    Directory of Open Access Journals (Sweden)

    Akira Katoh

    Full Text Available To optimize motor performance, both the amplitude and temporal properties of movements should be modifiable by motor learning. Here we report that the modification of movement timing is highly dependent on signaling through P/Q-type voltage-dependent calcium channels. Two lines of mutant mice heterozygous for P/Q-type voltage-dependent calcium channels exhibited impaired plasticity of eye movement timing, but relatively intact plasticity of movement amplitude during motor learning in the vestibulo-ocular reflex. The results thus demonstrate a distinction between the molecular signaling pathways regulating the timing versus amplitude of movements.

  1. Calcium channel antagonist and beta-blocker overdose: antidotes and adjunct therapies.

    Science.gov (United States)

    Graudins, Andis; Lee, Hwee Min; Druda, Dino

    2016-03-01

    Management of cardiovascular instability resulting from calcium channel antagonist (CCB) or beta-adrenergic receptor antagonist (BB) poisoning follows similar principles. Significant myocardial depression, bradycardia and hypotension result in both cases. CCBs can also produce vasodilatory shock. Additionally, CCBs, such as verapamil and diltiazem, are commonly ingested in sustained-release formulations. This can also be the case for some BBs. Peak toxicity can be delayed by several hours. Provision of early gastrointestinal decontamination with activated charcoal and whole-bowel irrigation might mitigate this. Treatment of shock requires a multimodal approach to inotropic therapy that can be guided by echocardiographic or invasive haemodynamic assessment of myocardial function. High-dose insulin euglycaemia is commonly recommended as a first-line treatment in these poisonings, to improve myocardial contractility, and should be instituted early when myocardial dysfunction is suspected. Catecholamine infusions are complementary to this therapy for both inotropic and chronotropic support. Catecholamine vasopressors and vasopressin are used in the treatment of vasodilatory shock. Optimizing serum calcium concentration can confer some benefit to improving myocardial function and vascular tone after CCB poisoning. High-dose glucagon infusions have provided moderate chronotropic and inotropic benefits in BB poisoning. Phosphodiesterase inhibitors and levosimendan have positive inotropic effects but also produce peripheral vasodilation, which can limit blood pressure improvement. In cases of severe cardiogenic shock and/or cardiac arrest post-poisoning, extracorporeal cardiac assist devices have resulted in successful recovery. Other treatments used in refractory hypotension include intravenous lipid emulsion for lipophilic CCB and BB poisoning and methylene blue for refractory vasodilatory shock. PMID:26344579

  2. Microdamage induced calcium efflux from bone matrix activates intracellular calcium signaling in osteoblasts via L-type and T-type voltage-gated calcium channels.

    Science.gov (United States)

    Jung, Hyungjin; Best, Makenzie; Akkus, Ozan

    2015-07-01

    Mechanisms by which bone microdamage triggers repair response are not completely understood. It has been shown that calcium efflux ([Ca(2+)]E) occurs from regions of bone undergoing microdamage. Such efflux has also been shown to trigger intracellular calcium signaling ([Ca(2+)]I) in MC3T3-E1 cells local to damaged regions. Voltage-gated calcium channels (VGCCs) are implicated in the entry of [Ca(2+)]E to the cytoplasm. We investigated the involvement of VGCC in the extracellular calcium induced intracellular calcium response (ECIICR). MC3T3-E1 cells were subjected to one dimensional calcium efflux from their basal aspect which results in an increase in [Ca(2+)]I. This increase was concomitant with membrane depolarization and it was significantly reduced in the presence of Bepridil, a non-selective VGCC inhibitor. To identify specific type(s) of VGCC in ECIICR, the cells were treated with selective inhibitors for different types of VGCC. Significant changes in the peak intensity and the number of [Ca(2+)]I oscillations were observed when L-type and T-type specific VGCC inhibitors (Verapamil and NNC55-0396, respectively) were used. So as to confirm the involvement of L- and T-type VGCC in the context of microdamage, cells were seeded on devitalized notched bone specimen, which were loaded to induce microdamage in the presence and absence of Verapamil and NNC55-0396. The results showed significant decrease in [Ca(2+)]I activity of cells in the microdamaged regions of bone when L- and T-type blockers were applied. This study demonstrated that extracellular calcium increase in association with damage depolarizes the cell membrane and the calcium ions enter the cell cytoplasm by L- and T-type VGCCs.

  3. Membrane Incorporation, Channel Formation, and Disruption of Calcium Homeostasis by Alzheimer's β-Amyloid Protein

    Directory of Open Access Journals (Sweden)

    Masahiro Kawahara

    2011-01-01

    Full Text Available Oligomerization, conformational changes, and the consequent neurodegeneration of Alzheimer's β-amyloid protein (AβP play crucial roles in the pathogenesis of Alzheimer's disease (AD. Mounting evidence suggests that oligomeric AβPs cause the disruption of calcium homeostasis, eventually leading to neuronal death. We have demonstrated that oligomeric AβPs directly incorporate into neuronal membranes, form cation-sensitive ion channels (“amyloid channels”, and cause the disruption of calcium homeostasis via the amyloid channels. Other disease-related amyloidogenic proteins, such as prion protein in prion diseases or α-synuclein in dementia with Lewy bodies, exhibit similarities in the incorporation into membranes and the formation of calcium-permeable channels. Here, based on our experimental results and those of numerous other studies, we review the current understanding of the direct binding of AβP into membrane surfaces and the formation of calcium-permeable channels. The implication of composition of membrane lipids and the possible development of new drugs by influencing membrane properties and attenuating amyloid channels for the treatment and prevention of AD is also discussed.

  4. Mechanosensory calcium-selective cation channels in epidermal cells

    Science.gov (United States)

    Ding, J. P.; Pickard, B. G.

    1993-01-01

    This paper explores the properties and likely functions of an epidermal Ca(2+)-selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co-channels can open together. Open time for co-channel quadruplets and quintuplets tends to be relatively long with millimolar Mg2+ (but not millimolar Ca2+) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is sychronized in rhythmic pulses. Certain lanthanides and a cytoskeleton-disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl-N-phenylcarbamate promotes tension-dependent activity at micromolar levels. With moderate suction, Gd3+ provided at about 0.5 micromole at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1-2 micromoles promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La3+, a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechanosensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall-membrane-cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall-membrane-cytoskeleton system experiences mechanical stress.

  5. TMEM16A is associated with voltage-gated calcium channels in mouse retina and its function is disrupted upon mutation of the auxiliary α2δ4 subunit

    Science.gov (United States)

    Caputo, Antonella; Piano, Ilaria; Demontis, Gian Carlo; Bacchi, Niccolò; Casarosa, Simona; Santina, Luca Della; Gargini, Claudia

    2015-01-01

    Photoreceptors rely upon highly specialized synapses to efficiently transmit signals to multiple postsynaptic targets. Calcium influx in the presynaptic terminal is mediated by voltage-gated calcium channels (VGCC). This event triggers neurotransmitter release, but also gates calcium-activated chloride channels (TMEM), which in turn regulate VGCC activity. In order to investigate the relationship between VGCC and TMEM channels, we analyzed the retina of wild type (WT) and Cacna2d4 mutant mice, in which the VGCC auxiliary α2δ4 subunit carries a nonsense mutation, disrupting the normal channel function. Synaptic terminals of mutant photoreceptors are disarranged and synaptic proteins as well as TMEM16A channels lose their characteristic localization. In parallel, calcium-activated chloride currents are impaired in rods, despite unaltered TMEM16A protein levels. Co-immunoprecipitation revealed the interaction between VGCC and TMEM16A channels in the retina. Heterologous expression of these channels in tsA-201 cells showed that TMEM16A associates with the CaV1.4 subunit, and the association persists upon expression of the mutant α2δ4 subunit. Collectively, our experiments show association between TMEM16A and the α1 subunit of VGCC. Close proximity of these channels allows optimal function of the photoreceptor synaptic terminal under physiological conditions, but also makes TMEM16A channels susceptible to changes occurring to calcium channels. PMID:26557056

  6. Calcium-Activated Potassium Channels at Nodes of Ranvier Secure Axonal Spike Propagation

    Directory of Open Access Journals (Sweden)

    Jan Gründemann

    2015-09-01

    Full Text Available Functional connectivity between brain regions relies on long-range signaling by myelinated axons. This is secured by saltatory action potential propagation that depends fundamentally on sodium channel availability at nodes of Ranvier. Although various potassium channel types have been anatomically localized to myelinated axons in the brain, direct evidence for their functional recruitment in maintaining node excitability is scarce. Cerebellar Purkinje cells provide continuous input to their targets in the cerebellar nuclei, reliably transmitting axonal spikes over a wide range of rates, requiring a constantly available pool of nodal sodium channels. We show that the recruitment of calcium-activated potassium channels (IK, KCa3.1 by local, activity-dependent calcium (Ca2+ influx at nodes of Ranvier via a T-type voltage-gated Ca2+ current provides a powerful mechanism that likely opposes depolarizing block at the nodes and is thus pivotal to securing continuous axonal spike propagation in spontaneously firing Purkinje cells.

  7. Effect of propionyl-L-carnitine on L-type calcium channels in human heart sarcolemma

    International Nuclear Information System (INIS)

    Propionyl-L-carnitine (PC) protects perfused rat hearts against damage by ischemia-reperfusion. Activation of L-type calcium channel play a role on ischemia-reperfusion damage. Therefore, we studied the effect of PC on some properties of L-type calcium channels in an in vitro preparation from human myocardium sarcolemma (from patients with idiopathic dilated cardiomyopathy). Binding of the L-type calcium channel blockers isradipine [3H]-PN 200-110 (PN) to plasma membrane preparations revealed a single population of binding sites (total number: Bmax = 213 +/- 34 fM/mg protein and affinity: Kd = 152 +/- 19 nM; n = 6). The characteristics of these binding sites were evaluated in the presence and in the absence of Ca2+ and of calcium blockers (D-888, a verapamillike drug, and diltiazem). Incubation in a Ca2+-containing buffer increased the affinity of PN binding sites. Binding sites for PN were modulated by organic calcium channel blockers; in competition isotherms at 37 degree C, D-888 (desmethoxyverapamil) decreased the PN binding, whereas diltiazem increased it. These results strongly suggest that the site labelled by PN is the voltage-operated calcium channel of the human myocardium. The addition of PC (1 mM) to plasma membranes labelled with PN at 37 degree C decreased the affinity of the binding; this effect was counteracted by the addition of Ca2+ to the medium. This result was consistent with a competition between Ca2+ and PC. The effect of PC incubation at 4 degree C was the opposite; at this temperature PC increased the affinity of the binding sites and the effect was obscured by Ca2+

  8. Novel 5-substituted benzyloxy-2-arylbenzofuran-3-carboxylic acids as calcium activated chloride channel inhibitors

    OpenAIRE

    Kumar, Satish; Namkung, Wan; A S Verkman; Sharma, Pawan K

    2012-01-01

    Transmembrane protein 16A (TMEM16A) channels are recently discovered membrane proteins that functions as a calcium activated chloride channel (CaCC). CaCCs are major regulators of various physiological processes, such as sensory transduction, epithelial secretion, smooth muscle contraction and oocyte fertilization. Thirty novel 5-substituted benzyloxy-2-arylbenzofuran-3-carboxylic acids (B01–B30) were synthesized and evaluated for their TMEM16A inhibitory activity by using short circuit curre...

  9. Identifying Calcium Channels and Porters in Plant Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Sze, Heven

    1998-04-01

    The overall objectives of the proposal submitted in 6/90 was to understand how Ca was transported across plant membranes, and how these transport pathways were regulated. Ca participates in many cellular processes, including the transduction of hormonal and environmental signals, secretion, and protein folding. These processes depend on the coordination of passive Ca fluxes via channels and active Ca pumps; however these transport pathways are poorly understood in plants. We had, therefore, proposed to identify and characterize Ca transport proteins, such as the inositol-1 ,4,5-trisphosphate (IP3)-sensitive Ca channels and Ca pumps. We have had difficulties characterizing and cloning the IP3-sensitive Ca channel, but have made considerable progress on the biochemical characterization, and partial purification of a 120 kD Ca-pumping ATPase. We have begun to determine the structure of Ca pumps by molecular cloning and have already obtained a partial cDNA with features characteristic of Ca pumps.

  10. The calcium-activated potassium channels of turtle hair cells

    OpenAIRE

    1995-01-01

    A major factor determining the electrical resonant frequency of turtle cochlear hair cells is the time course of the Ca-activated K current (Art, J. J., and R. Fettiplace. 1987. Journal of Physiology. 385:207- 242). We have examined the notion that this time course is dictated by the K channel kinetics by recording single Ca-activated K channels in inside-out patches from isolated cells. A hair cell's resonant frequency was estimated from its known correlation with the dimensions of the hair ...

  11. Anoctamin Calcium-Activated Chloride Channels May Modulate Inhibitory Transmission in the Cerebellar Cortex.

    Directory of Open Access Journals (Sweden)

    Weiping Zhang

    Full Text Available Calcium-activated chloride channels of the anoctamin (alias TMEM16 protein family fulfill critical functions in epithelial fluid transport, smooth muscle contraction and sensory signal processing. Little is known, however, about their contribution to information processing in the central nervous system. Here we examined the recent finding that a calcium-dependent chloride conductance impacts on GABAergic synaptic inhibition in Purkinje cells of the cerebellum. We asked whether anoctamin channels may underlie this chloride conductance. We identified two anoctamin channel proteins, ANO1 and ANO2, in the cerebellar cortex. ANO1 was expressed in inhibitory interneurons of the molecular layer and the granule cell layer. Both channels were expressed in Purkinje cells but, while ANO1 appeared to be retained in the cell body, ANO2 was targeted to the dendritic tree. Functional studies confirmed that ANO2 was involved in a calcium-dependent mode of ionic plasticity that reduces the efficacy of GABAergic synapses. ANO2 channels attenuated GABAergic transmission by increasing the postsynaptic chloride concentration, hence reducing the driving force for chloride influx. Our data suggest that ANO2 channels are involved in a Ca2+-dependent regulation of synaptic weight in GABAergic inhibition. Thus, in balance with the chloride extrusion mechanism via the co-transporter KCC2, ANO2 appears to regulate ionic plasticity in the cerebellum.

  12. David J. Triggle: Medicinal chemistry, to pharmacology, calcium channels, and beyond.

    Science.gov (United States)

    Walker, Michael J A

    2015-11-15

    David Triggle's scientific career began as a chemist, went through medicinal chemistry into pharmacology, and finally on to somewhat more philosophical interests in later years. It was a career marked by many contributions to all of those aspects of science. Chief amongst his many contributions, in addition to those in medicinal chemistry, was his work on the drugs known as calcium ion channel blockers or (calcium antagonists). In the calcium ion channel field he was a particularly instrumental figure in sorting out the mechanisms, actions and roles of the class of calcium channel blockers, known chemical and pharmacologically as the dihydropyridines (DHPs) in particular, as well as other calcium blockers of diverse structures. During the course of a long career, and extensive journeys into medicinal chemistry and pharmacology, he published voluminously in terms of papers, reviews, conference proceedings and books. Notably, many of his papers often had limited authorship where, as senior author it reflected his deep involvement in all aspects of the reported work. His work always helped clarify the field while his incisive reviews, together with his role in coordinating and running scientific meetings, were a great help in clarifying and organizing various fields of study. He has had a long and illustrious career, and is wellknown in the world of biomedical science; his contributions are appreciated, and well recognized everywhere. The following article attempts to chart a path through his work and contributions to medicinal chemistry, pharmacology, science, academia and students.

  13. Voltage-gated calcium channel and antisense oligonucleotides thereto

    Science.gov (United States)

    Hruska, Keith A. (Inventor); Friedman, Peter A. (Inventor); Barry, Elizabeth L. R. (Inventor); Duncan, Randall L. (Inventor)

    1998-01-01

    An antisense oligonucleotide of 10 to 35 nucleotides in length that can hybridize with a region of the .alpha..sub.1 subunit of the SA-Cat channel gene DNA or mRNA is provided, together with pharmaceutical compositions containing and methods utilizing such antisense oligonucleotide.

  14. EXAMINATION OF THE ANTICONVULSANT PROPERTIES OF VOLTAGE-SENSITIVE CALCIUM CHANNEL INHIBITORS IN AMYGDALA KINDLED SEIZURES

    Science.gov (United States)

    Representatives from three different classes of voltage-sensitive calcium (VSC) channel inhibitors were assessed for their protection against amygdala kindled seizures. dult male long Evans rats (n=12) were implanted with electrodes in the amygdala and were stimulated once daily ...

  15. L-type Voltage-Gated Calcium Channels in Conditioned Fear: A Genetic and Pharmacological Analysis

    Science.gov (United States)

    McKinney, Brandon C.; Sze, Wilson; White, Jessica A.; Murphy, Geoffrey G.

    2008-01-01

    Using pharmacological approaches, others have suggested that L-type voltage-gated calcium channels (L-VGCCs) mediate both consolidation and extinction of conditioned fear. In the absence of L-VGCC isoform-specific antagonists, we have begun to investigate the subtype-specific role of LVGCCs in consolidation and extinction of conditioned fear…

  16. [Discovering L-type calcium channels inhibitors of antihypertensive drugs based on drug repositioning].

    Science.gov (United States)

    Liang, Ying-xi; He, Yu-su; Jiang, Lu-di; Yue, Qiao-xin; Cui, Shuai; Bin, Li; Ye, Xiao-tong; Zhang, Xiao-hua; Zhang, Yang-ling

    2015-09-01

    This study was amid to construct the pharmacophore model of L-type calcium channel antagonist in the application of screening Drugbank and TCMD. This paper repositions the approved drugs resulting from virtual screening and discusses the relocation-based drug discovery methods, screening antihypertensive drugs with L-type calcium channel function from TCMD. Qualitative hypotheses wre generated by HipHop separately on the basis of 12 compounds with antagonistic action on L-type calcium channel expressed in rabbit cardiac muscle. Datebase searching method was used to evaluate the generated hypotheses. The optimum hypothesis was used to search Drugbank and TCMD. This paper repositions the approved drugs and evaluates the antihypertensive effect of the chemical constituent of traditional Chinese medicine resulting from virtual screening by the matching score and literature. The results showed that optimum qualitative hypothesis is with six features, which were two hydrogen-bond acceptors, four hydrophobic groups, and the CAI value of 2.78. Screening Drugbank achieves 93 approved drugs. Screening TCMD achieves 285 chemical constituents of traditional Chinese medicine. It was concluded that the hypothesis is reliable and can be used to screen datebase. The approved drugs resulting from virtual screening, such as pravastatin, are potentially L-type calcium channels inhibitors. The chemical constituents of traditional Chinese medicine, such as Arctigenin III and Arctigenin are potentially antihypertensive drugs. It indicates that Drug Repositioning based on hypothesis is possible. PMID:26983215

  17. [Discovering L-type calcium channels inhibitors of antihypertensive drugs based on drug repositioning].

    Science.gov (United States)

    Liang, Ying-xi; He, Yu-su; Jiang, Lu-di; Yue, Qiao-xin; Cui, Shuai; Bin, Li; Ye, Xiao-tong; Zhang, Xiao-hua; Zhang, Yang-ling

    2015-09-01

    This study was amid to construct the pharmacophore model of L-type calcium channel antagonist in the application of screening Drugbank and TCMD. This paper repositions the approved drugs resulting from virtual screening and discusses the relocation-based drug discovery methods, screening antihypertensive drugs with L-type calcium channel function from TCMD. Qualitative hypotheses wre generated by HipHop separately on the basis of 12 compounds with antagonistic action on L-type calcium channel expressed in rabbit cardiac muscle. Datebase searching method was used to evaluate the generated hypotheses. The optimum hypothesis was used to search Drugbank and TCMD. This paper repositions the approved drugs and evaluates the antihypertensive effect of the chemical constituent of traditional Chinese medicine resulting from virtual screening by the matching score and literature. The results showed that optimum qualitative hypothesis is with six features, which were two hydrogen-bond acceptors, four hydrophobic groups, and the CAI value of 2.78. Screening Drugbank achieves 93 approved drugs. Screening TCMD achieves 285 chemical constituents of traditional Chinese medicine. It was concluded that the hypothesis is reliable and can be used to screen datebase. The approved drugs resulting from virtual screening, such as pravastatin, are potentially L-type calcium channels inhibitors. The chemical constituents of traditional Chinese medicine, such as Arctigenin III and Arctigenin are potentially antihypertensive drugs. It indicates that Drug Repositioning based on hypothesis is possible.

  18. Inhibition of Escherichia coli chemotaxis by omega-conotoxin, a calcium ion channel blocker.

    OpenAIRE

    Tisa, L S; Olivera, B M; Adler, J

    1993-01-01

    Escherichia coli chemotaxis was inhibited by omega-conotoxin, a calcium ion channel blocker. With Tris-EDTA-permeabilized cells, nanomolar levels of omega-conotoxin inhibited chemotaxis without loss of motility. Cells treated with omega-conotoxin swam with a smooth bias, i.e., tumbling was inhibited.

  19. Regulation of the epithelial calcium channel TRPV5 by extracellular factors.

    NARCIS (Netherlands)

    Topala, C.N.; Bindels, R.J.M.; Hoenderop, J.G.J.

    2007-01-01

    PURPOSE OF REVIEW: Recent studies have greatly increased our knowledge concerning the regulation of renal calcium handling. This review focuses on newly identified calciotropic factors present in the pro-urine and the mechanisms by which they control the transient receptor potential channel vanilloi

  20. Nicotine enhancement of dopamine release by a calcium-dependent increase in the size of the readily releasable pool of synaptic vesicles.

    Science.gov (United States)

    Turner, Timothy J

    2004-12-15

    A major factor underlying compulsive tobacco use is nicotine-induced modulation of dopamine release in the mesolimbic reward pathway (Wise and Rompre, 1989). An established biochemical mechanism for nicotine-enhanced dopamine release is by activating presynaptic nicotinic acetylcholine receptors (nAChRs) (Wonnacott, 1997). Prolonged application of 10(-7) to 10(-5) m nicotine to striatal synaptosomes promoted a sustained efflux of [3H]dopamine. This nicotine effect was mediated by non-alpha7 nAChRs, because it was blocked by 5 mum mecamylamine but was resistant to 100 nm alpha-bungarotoxin (alphaBgTx). Dopamine release was diminished by omitting Na+ or by applying peptide calcium channel blockers, indicating that nAChRs trigger release by depolarizing the nerve terminals. However, because alpha7 receptors rapidly desensitize in the continuous presence of agonists, a repetitive stimulation protocol was used to evaluate the possible significance of desensitization. This protocol produced a transient increase in [3H]dopamine released by depolarization and a significant increase in the response to hypertonic solutions that measure the size of the readily releasable pool (RRP) of synaptic vesicles. The nicotine-induced increase in the size of the readily releasable pool was blocked by alphaBgTx and by the calmodulin antagonist calmidazolium, suggesting that Ca2+ entry through alpha7 nAChRs specifically enhances synaptic vesicle mobilization at dopamine terminals. Thus, nicotine enhances dopamine release by two complementary actions mediated by discrete nAChR subtypes and suggest that the alpha7 nAChR-mediated pathway is tightly and specifically coupled to refilling of the RRP of vesicles in dopamine terminals.

  1. Design, Synthesis and Structure-activity of N-Glycosyl-1-pyridyl-1H-pyrazole-5-carboxamide as Inhibitors of Calcium Channels

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yun-yun; LI Yu-xin; LI Yi-ming; YANG Xiao-ping; MAO Ming-zhen; LI Zheng-ming

    2013-01-01

    Carbohydrates,with broad-spectrum structures and biological functions,are key organic compounds in nature,along with nucleic acids and proteins.As part of our ongoing efforts to develop a new class of pesticides with novel mechanism of action,a series of novel N-glycosyl-l-pyridyl-lH-pyrazole-5-carboxamide was designed and synthesized via the reactions of glycosyl methanamides and pyridyl-pyrazole acid.The compounds were characterized by 1H NMR and 13C NMR.The bioassay results indicate that some of these compounds exhibit moderate insecticidal activities and assessed as potential inhibitors of calcium channels.The modulation of voltage-gated calcium channels by compounds 4a and 5a in the central neurons isolated from the third instar larvae of Spodoptera exigua was studied by whole-cell patch-clamp technique.In addition,compound 5a inhibits the recorded calcium currents reversible on washout.Experimental results also indicate that compound 5a did not release stored calcium from the Endoplasmic Reticulum.The present work demonstrates that N-glycosyl-l-pyridyl-lH-pyrazole-5-carboxamides cannot be used as possible inhibitors of calcium channels for developing novel pesticides.

  2. Role of Calcium Channels in Heavy Metal Toxicity

    OpenAIRE

    Carla Marchetti

    2013-01-01

    Cellular membranes are basically impermeable to ions and have developed specific pathways (channels, transporters or pumps) to facilitate metal translocation. These physiological carriers are not ideally selective and their specificity spectrum may include xenobiotic species, such as toxic metals whose availability in the environment has increased enormously in industrial times. I have studied the pathways of influx of two toxic metals, lead (Pb) and cadmium (Cd) in mammalian cells. Both meta...

  3. EFFECT OF ELECTROACUPUNCTURE AND CALCIUM-CHANNEL INHIBITORS ON CYTOPLASMIC FREE CALCIUM CONCENTRATION OF MOUSE BRAIN CELLS

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ming-mei; XIE Ji-min; CHEN Min; ZHANG Yan

    2005-01-01

    Objective: To study the effect of electroacupuncture (EA) and Verapamil and Nifedipine (calcium channel inhibitors) on free calcium concentrations of cells and intrasynaptosomes in hypothalamus (HT), periaqueductual grey matter (PAG) and hippocampus (HIP) of mice. Methods: The female ICR mice were randomly divided into control, EA, CaCl2 and CaCl2+EA groups (n=8 in each group). Pain threshold was detected by using radiation-heat irradiation-induced tail flick method. EA (8 Hz, a suitable stimulating strength, dense-sparse waves and duration of 30 min) was applied to"Shuigou" (水沟 GV 26) and "Chengjiang" (承浆CV 24). CaCl2 (10 μL, 0.2 μmol/L) was injected into the lateral cerebral ventricle of mice after EA. The concentrations of cytosolic free calcium ([Ca2+]i) in HIP, PAG, HT cell suspension specimen and hippocampal intrasynaptosome suspension of mice were determined by the fluorescent calcium indicator Fura-2-AM and a spectrofluorometer. Results: During EA analgesia, the intracellular free [Ca2+]i in HT and PAG specimens and intrsynaptosomal [Ca2+]i of the 3 cerebral regions decreased considerably (P<0.05~0.01), but that in hippocampal cell suspension increased significantly (P<0.01) in comparison with control group. The concentrations of hippocampal intrasynaptosomal free [Ca2+]i decreased significantly after adding Verapamil and Nifedipine to the extracted hippocampal intrasynaptosomal specimen. Microinjection of CaCl2 into lateral ventricle had no apparent influence on degree of analgesia (DA)% and intracellular and intrasynapsotomal [Ca2+]i, but significantly lower DA% and reduce changes of cytosolic and intrasynaptosomal [Ca2+]i induced by EA stimulation. Conclusion: Calcium ion in the neurons and intrasynaptosome of HT, PAG and HIP is involved in electroacupuncture analgesia.

  4. Hydrogen sulfide-induced itch requires activation of Cav3.2 T-type calcium channel in mice

    Science.gov (United States)

    Wang, Xue-Long; Tian, Bin; Huang, Ya; Peng, Xiao-Yan; Chen, Li-Hua; Li, Jun-Cheng; Liu, Tong

    2015-01-01

    The contributions of gasotransmitters to itch sensation are largely unknown. In this study, we aimed to investigate the roles of hydrogen sulfide (H2S), a ubiquitous gasotransmitter, in itch signaling. We found that intradermal injection of H2S donors NaHS or Na2S, but not GYY4137 (a slow-releasing H2S donor), dose-dependently induced scratching behavior in a μ-opioid receptor-dependent and histamine-independent manner in mice. Interestingly, NaHS induced itch via unique mechanisms that involved capsaicin-insensitive A-fibers, but not TRPV1-expressing C-fibers that are traditionally considered for mediating itch, revealed by depletion of TRPV1-expressing C-fibers by systemic resiniferatoxin treatment. Moreover, local application of capsaizapine (TRPV1 blocker) or HC-030031 (TRPA1 blocker) had no effects on NaHS-evoked scratching. Strikingly, pharmacological blockade and silencing of Cav3.2 T-type calcium channel by mibefradil, ascorbic acid, zinc chloride or Cav3.2 siRNA dramatically decreased NaHS-evoked scratching. NaHS induced robust alloknesis (touch-evoked itch), which was inhibited by T-type calcium channels blocker mibefradil. Compound 48/80-induced itch was enhanced by an endogenous precursor of H2S (L-cysteine) but attenuated by inhibitors of H2S-producing enzymes cystathionine γ-lyase and cystathionine β-synthase. These results indicated that H2S, as a novel nonhistaminergic itch mediator, may activates Cav3.2 T-type calcium channel, probably located at A-fibers, to induce scratching and alloknesis in mice. PMID:26602811

  5. Atypical calcium regulation of the PKD2-L1 polycystin ion channel.

    Science.gov (United States)

    DeCaen, Paul G; Liu, Xiaowen; Abiria, Sunday; Clapham, David E

    2016-01-01

    Native PKD2-L1 channel subunits are present in primary cilia and other restricted cellular spaces. Here we investigate the mechanism for the channel's unusual regulation by external calcium, and rationalize this behavior to its specialized function. We report that the human PKD2-L1 selectivity filter is partially selective to calcium ions (Ca(2+)) moving into the cell, but blocked by high internal Ca(2+)concentrations, a unique feature of this transient receptor potential (TRP) channel family member. Surprisingly, we find that the C-terminal EF-hands and coiled-coil domains do not contribute to PKD2-L1 Ca(2+)-induced potentiation and inactivation. We propose a model in which prolonged channel activity results in calcium accumulation, triggering outward-moving Ca(2+) ions to block PKD2-L1 in a high-affinity interaction with the innermost acidic residue (D523) of the selectivity filter and subsequent long-term channel inactivation. This response rectifies Ca(2+) flow, enabling Ca(2+) to enter but not leave small compartments such as the cilium. PMID:27348301

  6. Pharmacological blockade of voltage-gated calcium channels as a potential cardioprotective strategy

    OpenAIRE

    Pushparaj, Charumathi

    2014-01-01

    Voltage-gated Ca2+ channels (VGCCs) are essential for initiating and regulating cardiac function. During the cardiac action potential, Ca2+ influx through L-type channels triggers the sarcoplasmic reticulum Ca2+ release that enables the EC coupling. Ca2+ can also enter cardiac myocytes through low-voltage-activated T-type channels, which are expressed throughout cardiac development until the end of the neonatal period, and can contribute to pacemaker activity as well as EC coupling to some ex...

  7. A homology model of the pore domain of a voltage-gated calcium channel is consistent with available SCAM data

    OpenAIRE

    Bruhova, Iva; Zhorov, Boris S.

    2010-01-01

    In the absence of x-ray structures of calcium channels, their homology models are used to rationalize experimental data and design new experiments. The modeling relies on sequence alignments between calcium and potassium channels. Zhen et al. (2005. J. Gen. Physiol. doi:10.1085/jgp.200509292) used the substituted cysteine accessibility method (SCAM) to identify pore-lining residues in the Cav2.1 channel and concluded that their data are inconsistent with the symmetric architecture of the pore...

  8. Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate

    OpenAIRE

    Ivanov, Vadim; Ivanova, Svetlana; KALINOVSKY, TATIANA; NIEDZWIECKI, ALEKSANDRA; RATH, MATTHIAS

    2016-01-01

    Calcium, sodium and potassium channel blockers are widely prescribed medications for a variety of health problems, most frequently for cardiac arrhythmias, hypertension, angina pectoris and other disorders. However, chronic application of channel blockers is associated with numerous side effects, including worsening cardiac pathology. For example, nifedipine, a calcium-channel blocker was found to be associated with increased mortality and increased risk for myocardial infarction. In addition...

  9. Neuronal calcium channel antagonists. Discrimination between calcium channel subtypes using omega-conotoxin from Conus magus venom

    International Nuclear Information System (INIS)

    The omega-conotoxins from the venom of fish-hunting cone snails are probably the most useful of presently available ligands for neuronal Ca channels from vertebrates. Two of these peptide toxins, omega-conotoxins MVIIA and MVIIB from the venom of Conus magus, were purified. The amino acid sequences show significant differences from omega-conotoxins from Conus geographus. Total synthesis of omega-conotoxin MVIIA was achieved, and biologically active radiolabeled toxin was produced by iodination. Although omega-conotoxins from C. geographus (GVIA) and C. magus (MVIIA) appear to compete for the same sites in mammalian brain, in amphibian brain the high-affinity binding of omega-conotoxin MVIIA has narrower specificity. In this system, it is demonstrated that a combination of two omega-conotoxins can be used for biochemically defining receptor subtypes and suggested that these correspond to subtypes of neutronal Ca2+ channels

  10. Putative calcium-binding domains of the Caenorhabditis elegans BK channel are dispensable for intoxication and ethanol activation.

    Science.gov (United States)

    Davis, S J; Scott, L L; Ordemann, G; Philpo, A; Cohn, J; Pierce-Shimomura, J T

    2015-07-01

    Alcohol modulates the highly conserved, voltage- and calcium-activated potassium (BK) channel, which contributes to alcohol-mediated behaviors in species from worms to humans. Previous studies have shown that the calcium-sensitive domains, RCK1 and the Ca(2+) bowl, are required for ethanol activation of the mammalian BK channel in vitro. In the nematode Caenorhabditis elegans, ethanol activates the BK channel in vivo, and deletion of the worm BK channel, SLO-1, confers strong resistance to intoxication. To determine if the conserved RCK1 and calcium bowl domains were also critical for intoxication and basal BK channel-dependent behaviors in C. elegans, we generated transgenic worms that express mutated SLO-1 channels predicted to have the RCK1, Ca(2+) bowl or both domains rendered insensitive to calcium. As expected, mutating these domains inhibited basal function of SLO-1 in vivo as neck and body curvature of these mutants mimicked that of the BK null mutant. Unexpectedly, however, mutating these domains singly or together in SLO-1 had no effect on intoxication in C. elegans. Consistent with these behavioral results, we found that ethanol activated the SLO-1 channel in vitro with or without these domains. By contrast, in agreement with previous in vitro findings, C. elegans harboring a human BK channel with mutated calcium-sensing domains displayed resistance to intoxication. Thus, for the worm SLO-1 channel, the putative calcium-sensitive domains are critical for basal in vivo function but unnecessary for in vivo ethanol action.

  11. Zebrafish CaV2.1 calcium channels are tailored for fast synchronous neuromuscular transmission.

    Science.gov (United States)

    Naranjo, David; Wen, Hua; Brehm, Paul

    2015-02-01

    The CaV2.2 (N-type) and CaV2.1 (P/Q-type) voltage-dependent calcium channels are prevalent throughout the nervous system where they mediate synaptic transmission, but the basis for the selective presence at individual synapses still remains an open question. The CaV2.1 channels have been proposed to respond more effectively to brief action potentials (APs), an idea supported by computational modeling. However, the side-by-side comparison of CaV2.1 and CaV2.2 kinetics in intact neurons failed to reveal differences. As an alternative means for direct functional comparison we expressed zebrafish CaV2.1 and CaV2.2 α-subunits, along with their accessory subunits, in HEK293 cells. HEK cells lack calcium currents, thereby circumventing the need for pharmacological inhibition of mixed calcium channel isoforms present in neurons. HEK cells also have a simplified morphology compared to neurons, which improves voltage control. Our measurements revealed faster kinetics and shallower voltage-dependence of activation and deactivation for CaV2.1. Additionally, recordings of calcium current in response to a command waveform based on the motorneuron AP show, directly, more effective activation of CaV2.1. Analysis of calcium currents associated with the AP waveform indicate an approximately fourfold greater open probability (PO) for CaV2.1. The efficient activation of CaV2.1 channels during APs may contribute to the highly reliable transmission at zebrafish neuromuscular junctions. PMID:25650925

  12. Zebrafish CaV2.1 Calcium Channels Are Tailored for Fast Synchronous Neuromuscular Transmission

    Science.gov (United States)

    Naranjo, David; Wen, Hua; Brehm, Paul

    2015-01-01

    The CaV2.2 (N-type) and CaV2.1 (P/Q-type) voltage-dependent calcium channels are prevalent throughout the nervous system where they mediate synaptic transmission, but the basis for the selective presence at individual synapses still remains an open question. The CaV2.1 channels have been proposed to respond more effectively to brief action potentials (APs), an idea supported by computational modeling. However, the side-by-side comparison of CaV2.1 and CaV2.2 kinetics in intact neurons failed to reveal differences. As an alternative means for direct functional comparison we expressed zebrafish CaV2.1 and CaV2.2 α-subunits, along with their accessory subunits, in HEK293 cells. HEK cells lack calcium currents, thereby circumventing the need for pharmacological inhibition of mixed calcium channel isoforms present in neurons. HEK cells also have a simplified morphology compared to neurons, which improves voltage control. Our measurements revealed faster kinetics and shallower voltage-dependence of activation and deactivation for CaV2.1. Additionally, recordings of calcium current in response to a command waveform based on the motorneuron AP show, directly, more effective activation of CaV2.1. Analysis of calcium currents associated with the AP waveform indicate an approximately fourfold greater open probability (PO) for CaV2.1. The efficient activation of CaV2.1 channels during APs may contribute to the highly reliable transmission at zebrafish neuromuscular junctions. PMID:25650925

  13. Molecular Interactions between Tarantula Toxins and Low-Voltage-Activated Calcium Channels.

    Science.gov (United States)

    Salari, Autoosa; Vega, Benjamin S; Milescu, Lorin S; Milescu, Mirela

    2016-01-01

    Few gating-modifier toxins have been reported to target low-voltage-activated (LVA) calcium channels, and the structural basis of toxin sensitivity remains incompletely understood. Studies of voltage-gated potassium (Kv) channels have identified the S3b-S4 "paddle motif," which moves at the protein-lipid interface to drive channel opening, as the target for these amphipathic neurotoxins. Voltage-gated calcium (Cav) channels contain four homologous voltage sensor domains, suggesting multiple toxin binding sites. We show here that the S3-S4 segments within Cav3.1 can be transplanted into Kv2.1 to examine their individual contributions to voltage sensing and pharmacology. With these results, we now have a more complete picture of the conserved nature of the paddle motif in all three major voltage-gated ion channel types (Kv, Nav, and Cav). When screened with tarantula toxins, the four paddle sequences display distinct toxin binding properties, demonstrating that gating-modifier toxins can bind to Cav channels in a domain specific fashion. Domain III was the most commonly and strongly targeted, and mutagenesis revealed an acidic residue that is important for toxin binding. We also measured the lipid partitioning strength of all toxins tested and observed a positive correlation with their inhibition of Cav3.1, suggesting a key role for membrane partitioning. PMID:27045173

  14. Interference with Ca2+ release activated Ca2+ (CRAC) channel function delays T-cell arrest in vivo

    OpenAIRE

    Waite, Janelle C.; Vardhana, Santosh; Shaw, Patrick J.; Jang, Jung-Eun; McCarl, Christie-Ann; Cameron, Thomas O; Feske, Stefan; Dustin, Michael L

    2013-01-01

    Entry of lymphocytes into secondary lymphoid organs (SLOs) involves intravascular arrest and intracellular calcium ion ([Ca2+]i) elevation. TCR activation triggers increased [Ca2+]i and can arrest T-cell motility in vitro. However the requirement for [Ca2+]i elevation in arresting T cells in vivo has not been tested. Here, we have manipulated the Ca2+ release-activated Ca2+ (CRAC) channel pathway required for [Ca2+]i elevation in T cells through genetic deletion of stromal interaction molecul...

  15. A slow release calcium delivery system for the study of reparative dentine formation.

    Science.gov (United States)

    Hunter, A R; Kirk, E E; Robinson, D H; Kardos, T B

    1998-06-01

    Several liquid, semi-solid and solid delivery systems were formulated and tested to devise a method of reproducibly administering accurate micro-doses of calcium into a 700 microns diameter cavity in a rat maxillary incisor tooth, in the absence of hydroxyl ions. Development of this delivery system was necessary to facilitate studies of the mechanisms of pulpal repair and odontoblast differentiation. The principal requirements for the delivery system were that it should be easily administered into a small pulp exposure in the rat incisor and that a greater than 1000-fold range in calcium ion concentrations could be incorporated and delivered for a period of 2-3 days, preferably in an acidic environment to minimize the effect of non-specific nucleation under alkaline conditions. Poly- (ethylene) glycol microspheres were found to be an ideal vehicle. Under the in vitro dissolution conditions used, complete release of all calcium salts occurred within 12-15 hours, except for the very water-insoluble calcium stearate. It was anticipated that the release of calcium ions would be significantly more prolonged in vivo because of the physical constraints of the prepared cavity as well as the restricted access to fluid flow. PMID:9863419

  16. Functional Importance of L- and P/Q-Type Voltage-Gated Calcium Channels in Human Renal Vasculature

    DEFF Research Database (Denmark)

    Hansen, Pernille B; Poulsen, Christian B; Walter, Steen;

    2011-01-01

    revealed signals for Ca(v) 2.1 and Ca(v) 3.1 associated with smooth muscle cells of preglomerular and postglomerular vessels. In human intrarenal arteries, depolarization with potassium induced a contraction inhibited by the L-type antagonist nifedipine, EC(50) 1.2×10(-8) mol/L. The T-type antagonist...... L- and P/Q-type channels are of functional importance for the depolarization-induced vasoconstriction. The contribution of P/Q-type channels to contraction in the human vasculature is a novel mechanism for the regulation of renal blood flow and suggests that clinical treatment with calcium blockers......Calcium channel blockers are widely used for treatment of hypertension, because they decrease peripheral vascular resistance through inhibition of voltage-gated calcium channels. Animal studies of renal vasculature have shown expression of several types of calcium channels that are involved in...

  17. GABA(A) Increases Calcium in Subventricular Zone Astrocyte-Like Cells Through L- and T-Type Voltage-Gated Calcium Channels

    DEFF Research Database (Denmark)

    Young, Stephanie Z; Platel, Jean-Claude; Nielsen, Jakob V;

    2010-01-01

    induced Ca(2+) increases in 40-50% of SVZ astrocytes. GABA(A)-induced Ca(2+) increases were prevented with nifedipine and mibefradil, blockers of L- and T-type voltage-gated calcium channels (VGCC). The L-type Ca(2+) channel activator BayK 8644 increased the percentage of GABA(A)-responding astrocyte...

  18. ATP releasing connexin 30 hemichannels mediate flow-induced calcium signaling in the collecting duct

    DEFF Research Database (Denmark)

    Svenningsen, Per; Burford, James L; Peti-Peterdi, János

    2013-01-01

    ATP in the renal tubular fluid is an important regulator of salt and water reabsorption via purinergic calcium signaling that involves the P2Y2 receptor, ENaC, and AQP2. Recently, we have shown that connexin (Cx) 30 hemichannels are localized to the non-junctional apical membrane of cells...... by suramin. Taken together, these data confirm that mechanosensitive Cx30 hemichannels mediate tubular ATP release and purinergic calcium signaling in the CD which mechanism plays an important role in the regulation of CD salt and water reabsorption....

  19. Ryanodine receptors, a family of intracellular calcium ion channels, are expressed throughout early vertebrate development

    Directory of Open Access Journals (Sweden)

    Wu Houdini HT

    2011-12-01

    Full Text Available Abstract Background Calcium signals ([Ca2+]i direct many aspects of embryo development but their regulation is not well characterised. Ryanodine receptors (RyRs are a family of intracellular Ca2+ release channels that control the flux of Ca2+ from internal stores into the cytosol. RyRs are primarily known for their role in excitation-contraction coupling in adult striated muscle and ryr gene mutations are implicated in several human diseases. Current evidence suggests that RyRs do not have a major role to play prior to organogenesis but regulate tissue differentiation. Findings The sequences of the five zebrafish ryr genes were confirmed, their evolutionary relationship established and the primary sequences compared to other vertebrates, including humans. RyRs are differentially expressed in slow (ryr1a, fast (ryr3 and both types (ryr1b of developing skeletal muscle. There are two ryr2 genes (ryr2a and ryr2b which are expressed exclusively in developing CNS and cardiac tissue, respectively. In addition, ryr3 and ryr2a mRNA is detectable in the initial stages of development, prior to embryonic axis formation. Conclusions Our work reveals that zebrafish ryr genes are differentially expressed throughout the developing embryo from cleavage onwards. The data suggests that RyR-regulated Ca2+ signals are associated with several aspects of embryonic development, from organogenesis through to the differentiation of the musculoskeletal, cardiovascular and nervous system. These studies will facilitate further work to explore the developmental function of RyRs in each of these tissue types.

  20. Pinaverium acts as L-type calcium channel blocker on smooth muscle of colon.

    Science.gov (United States)

    Malysz, J; Farraway, L A; Christen, M O; Huizinga, J D

    1997-08-01

    The effect of pinaverium was electrophysiologically characterized and compared with the established L-type calcium channel blockers diltiazem, D600, and nitrendipine on canine colonic circular smooth muscle. Effects were studied on the electrical activity of the smooth muscle cells, in particular the spontaneously occurring slow wave. In addition, effects were examined on spontaneous contraction patterns and contractile activities generated by stimulation of cholinergic nerves or directly by stimulating muscarinic receptors. Effects were also examined on excitation of NO-releasing intrinsic nerves. Pinaverium bromide affected the slow wave by selectively inhibiting the plateau potential that is associated with generation of contractile activity. Pinaverium, similar to diltiazem and D600, produced reductions in cholinergic responses as well as spontaneous contractions. The IC50 values for inhibition of cholinergic responses for pinaverium, diltiazem, and D600 were 1.0 x 10(-6), 4.1 x 10(-7), and 5.3 x 10(-7) M, respectively. The IC50 values for inhibition of spontaneous contractile activity for pinaverium, diltiazem, and D600 were 3.8 x 10(-6), 9.7 x 10(-7), and 8.0 x 10(-7) M, respectively. Increases in contractility by carbachol were abolished by pretreatment with either pinaverium or D600. In addition, neither pinaverium nor D600 had any effects on the inhibitory NO-mediated relaxations. These data provide a rationale for the use of pinaverium in the treatment of colonic motor disorders where excessive contraction has to be suppressed. PMID:9360010

  1. Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Kozuka, M.; Ito, T.; Hirose, S.; Takahashi, K.; Hagiwara, H.

    1989-02-28

    Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using /sup 125/I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent.

  2. Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

    International Nuclear Information System (INIS)

    Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using 125I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent

  3. Aluminium and hydrogen ions inhibit a mechanosensory calcium-selective cation channel

    Science.gov (United States)

    Ding, J. P.; Pickard, B. G.

    1993-01-01

    The tension-dependent activity of mechanosensory calcium-selective cation channels in excised plasmalemmal patches from onion bulb scale epidermis is modulated by pH in the physiologically meaningful range between 4.5 and 7.2. It is rapidly lowered by lowering pH and rapidly raised by raising pH. Channel activity is effectively inhibited by low levels of aluminium ions and activity can be partially restored by washing for a few minutes. We suggest that under normal conditions the sensitivity of the mechanosensory channels to pH of the wall free space plays important roles in regulation of plant activities such as growth. We further suggest that, when levels of acid and aluminium ions in the soil solution are high, they might inhibit similar sensory channels in cells of the root tip, thus contributing critically to the acid soil syndrome.

  4. Preparation of calcium chloride-loaded solid lipid particles and heat-triggered calcium ion release

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Huangying; Kim, Jin-Chul [Kangwon National University, Chunchon (Korea, Republic of)

    2015-08-15

    CaCl{sub 2}-loaded solid lipid particles (SLPs) were prepared by a melt/emulsification/solidification method. CaCl{sub 2} microparticles (1-5 μm) could be obtained in a mortar with aid of the dispersant (Tween 80/Span80 (35/65, w/w)) when the ratio of CaCl{sub 2} to dispersant was 2 : 0.1 (w/w). SLP was prepared by dispersing 0.42 g of micronized CaCl{sub 2} particles in 2 g of molten PBSA, emulsifying the mixture at 85 .deg. C in 40 ml of Tween 20 solution (0.5% w/v), and quenching the emulsion in an ice bath. The diameter of CaCl{sub 2}-loaded SLP was 10-150 μm. The unenveloped CaCl{sub 2} could be removed by dialysis and the specific loading of CaCl{sub 2} in SLP was 0.036mg/mg. An EDS spectrum of CaCl{sub 2}-loaded SLP, which was dialyzed, showed that the unenveloped CaCl{sub 2} was completely removed. Any excipients (dispersant, Tween 20, CaCl{sub 2}) had little effect on the melting point of SLPs. No appreciable amount of Ca2+ was released in 20-50 .deg. C for 22 h. But the release degree at 60 .deg. C was significant (about 2.3%) during the same period. The matrix of the lipid particle was in a liquid state at 60 .deg. C, so CaCl{sub 2} particles could move freely and contact the surrounding water, leading to the release. At 70 .deg. C, the release degree at a given time was a few times higher than that obtained at 60 .deg. C.

  5. A combined role of calcium channel blockers and angiotensin receptor blockers in stroke prevention

    Directory of Open Access Journals (Sweden)

    Ji-Guang Wang

    2009-07-01

    Full Text Available Ji-Guang WangCentre for Epidemiological Studies and Clinical Trials, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, ChinaAbstract: Stroke is a leading cause of death and disability worldwide. The importance of lowering blood pressure for reducing the risk of stroke is well established. However, not all the benefits of antihypertensive treatments in stroke can be accounted for by reductions in BP and there may be differences between antihypertensive classes as to which provides optimal protection. Dihydropyridine calcium channel blockers, such as amlodipine, and angiotensin receptor blockers, such as valsartan, represent the two antihypertensive drug classes with the strongest supportive data for the prevention of stroke. Therefore, when combination therapy is required, a combination of these two antihypertensive classes represents a logical approach.Keywords: stroke, angiotensin, calcium channel, cerebrovascular, hypertension, blood pressure

  6. Induction of gingival hyperplasia associated with the use of calcium channel blockers

    Directory of Open Access Journals (Sweden)

    Daniela Fernandes de SOUZA

    2009-12-01

    Full Text Available Introduction: Calcium channel blockers are drugs that can modify the gingival tissues response to inflammatory processes in the presence of dental plaque, inducing gingival overgrowth. Preexisting gingival inflammation induced by dental plaque seems to be a favorable condition to the development and/or expression of gingival overgrowth. Objective, case report and conclusion: The aim of this study was to report a clinical case of injury produced by dental plaque and its consequent gingival alteration that were exacerbated due to calcium channel blockers use. It was concluded that periodontal surgery is appropriate only when the control of dental plaque and/or replacement of the drug by another medicine do not provide the expected results.

  7. Direct recording and molecular identification of the calcium channel of primary cilia

    Science.gov (United States)

    Decaen, Paul G.; Delling, Markus; Vien, Thuy N.; Clapham, David E.

    2013-12-01

    A primary cilium is a solitary, slender, non-motile protuberance of structured microtubules (9+0) enclosed by plasma membrane. Housing components of the cell division apparatus between cell divisions, primary cilia also serve as specialized compartments for calcium signalling and hedgehog signalling pathways. Specialized sensory cilia such as retinal photoreceptors and olfactory cilia use diverse ion channels. An ion current has been measured from primary cilia of kidney cells, but the responsible genes have not been identified. The polycystin proteins (PC and PKD), identified in linkage studies of polycystic kidney disease, are candidate channels divided into two structural classes: 11-transmembrane proteins (PKD1, PKD1L1 and PKD1L2) remarkable for a large extracellular amino terminus of putative cell adhesion domains and a G-protein-coupled receptor proteolytic site, and the 6-transmembrane channel proteins (PKD2, PKD2L1 and PKD2L2; TRPPs). Evidence indicates that the PKD1 proteins associate with the PKD2 proteins via coiled-coil domains. Here we use a transgenic mouse in which only cilia express a fluorophore and use it to record directly from primary cilia, and demonstrate that PKD1L1 and PKD2L1 form ion channels at high densities in several cell types. In conjunction with an accompanying manuscript, we show that the PKD1L1-PKD2L1 heteromeric channel establishes the cilia as a unique calcium compartment within cells that modulates established hedgehog pathways.

  8. Inhibition of Recombinant Human T-type Calcium Channels by Δ9-Tetrahydrocannabinol and Cannabidiol*

    OpenAIRE

    Ross, Hamish Redmond; Napier, Ian; Connor, Mark

    2008-01-01

    Δ9-Tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most prevalent biologically active constituents of Cannabis sativa. THC is the prototypic cannabinoid CB1 receptor agonist and is psychoactive and analgesic. CBD is also analgesic, but it is not a CB1 receptor agonist. Low voltage-activated T-type calcium channels, encoded by the CaV3 gene family, regulate the excitability of many cells, including neurons involved in nociceptive processing. We examined the eff...

  9. Calcium-channel blockers for the prevention of stroke: from scientific evidences to the clinical practice

    Directory of Open Access Journals (Sweden)

    S. Taddei

    2013-05-01

    Full Text Available AIM OF THE REVIEW The present review aims to analyze the role of calcium-channel blockers, and particularly newer molecules, as first-line therapy for cerebrovascular disease. BACKGROUND Stroke is the leading cause of disability in the general population. Among traditional cardiovascular risk factors, hypertension has a key role in the genesis of both hemorrhagic and ischemic stroke and a direct correlation exists between blood pressure values and the risk of stroke. Moreover, blood pressure reduction has been demonstrated to be the most important route to reduce stroke incidence and recurrence. However, the mere reduction of blood pressure values does not normalize the cardiovascular risk of the hypertensive patient. It is therefore necessary to use drug classes that beyond their blood pressure-lowering effect have also an additional effect in terms of organ protection. Among these, calcium-channel blockers have a crucial profile. Firstly, they are effective in inducing left ventricular hypertrophy regression, with a strength at least equal to that of ACE-inhibitors. Secondly, they have an antithrombotic and an endothelium-protecting effect, mediated by their antioxidant activity. Finally, calcium-channel blockers are the most powerful drugs in preventing vascular remodeling. For these reasons this drug class has probably the strongest antiatherosclerotic effect, and it is the first-choice treatment mainly for cerebrovascular disease. Among different available calcium-channel blockers, the newer ones seem to possess pharmacokinetic characteristics allowing a more homogeneous 24 hours coverage as compared to older molecules, and preliminary data seem to suggest a greater beneficial effect also on left ventricular hypertrophy and lower incidence of side effects. CONCLUSIONS Although blood pressure reduction is the main tool to reduce cerebrovascular risk in hypertensive patients, some drug classes, such as calciumchannel blockers, seem to provide

  10. Solution structure of the calcium channel antagonist omega-conotoxin GVIA.

    OpenAIRE

    Skalicky, J. J.; Metzler, W. J.; Ciesla, D. J.; Galdes, A.; Pardi, A

    1993-01-01

    The three-dimensional solution structure is reported for omega-conotoxin GVIA, which is a potent inhibitor of presynaptic calcium channels in vertebrate neuromuscular junctions. Structures were generated by a hybrid distance geometry and restrained molecular dynamics approach using interproton distance, torsion angle, and hydrogen-bonding constraints derived from 1H NMR data. Conformations of GVIA with low constraint violations converged to a common peptide fold. The secondary structure in th...

  11. Applying Theoretical Approach for Predicting the Selective Calcium Channel Blockers Pharmacological Parameter by Biopartitioning Micellar Chromatography

    Institute of Scientific and Technical Information of China (English)

    WANG Su-Min; YANG Geng-Liang; LI Zhi-Wei; LIU Hai-Yan; GUO Hui-Juan

    2006-01-01

    The usefulness of biopartitioning micellar chromatography (BMC) for predicting oral drug acute toxicity and apparent bioavailability was demonstrated. A logarithmic model (an LD50 model) and the second order polynomial models (apparent bioavailability model) have been obtained using the retention data of the selective calcium channel blockers to predict pharmacological properties of compounds. The use of BMC is simple, reproducible and can provide key information about the acute toxicity and transport properties of new compounds during the drug discovery process.

  12. Effects of calcium channel blocker, nifedipine, on antidepressant activity of fluvoxamine, venlafaxine and tianeptine in mice

    OpenAIRE

    SHARMA, Ashok K.; Anjan Khadka; Navdeep Dahiya

    2015-01-01

    Background: Cardiovascular diseases are commonly associated with depression. Calcium channel blockers (CCBs) form commonly used group of drugs for the treatment of a number of cardiovascular diseases. Nifedipine, a CCB, has been shown to possess antidepressant activity and potentiate antidepressant activity of imipramine and sertraline, however, literature on its interaction with newer antidepressant drugs such as fluvoxamine, venlafaxine and tianeptine is limited. Hence, the present study wa...

  13. Role of T-type calcium channels in myogenic tone of skeletal muscle resistance arteries

    DEFF Research Database (Denmark)

    VanBavel, Ed; Sorop, Oana; Andreasen, Ditte;

    2002-01-01

    T-type calcium channels may be involved in the maintenance of myogenic tone. We tested their role in isolated rat cremaster arterioles obtained after CO(2) anesthesia and decapitation. Total RNA was analyzed by RT-PCR and Southern blotting for calcium channel expression. We observed expression...... of voltage-operated calcium (Ca(V)) channels Ca(V)3.1 (T-type), Ca(V)3.2 (T-type), and Ca(V)1.2 (L-type) in cremaster arterioles (n = 3 rats). Amplification products were observed only in the presence of reverse transcriptase and cDNA. Concentration-response curves of the relatively specific L-type blocker...... verapamil and the relatively specific T-type blockers mibefradil and nickel were made on cannulated vessels with either myogenic tone (75 mmHg) or a similar level of constriction induced by 30 mM K(+) at 35 mmHg. Mibefradil and nickel were, respectively, 162-fold and 300-fold more potent in inhibiting...

  14. Deltamethrin Inhibits the Human T-type Voltage-Sensitive Calcium Channel (Cav3.2

    Directory of Open Access Journals (Sweden)

    Steven B. Symington

    2009-01-01

    Full Text Available The goal of this study was to determine the effect of deltamethrin, a pyrethroid insecticide, on CaV3.2, a human T-type voltage-sensitive calcium channel expressed in Xenopus laevis (X.laevis oocytes. Cav3.2 cDNA was transcribed into cRNA; the cRNA was then injected into X.laevis oocytes and electrophysiologically characterized using the two-electrode voltage clamp technique with Ba2+ as a charge carrier. Deltamethrin (10-7 M reduced peak current in a nonreversible manner compared to the untreated control, but had no effect on the voltagedependent activation and inactivation kinetics. These findings confirm that human CaV3.2 is a target for deltamethrin and quite possibly other pyrethroid insecticides. These studies provide insight into the molecular mechanisms of the effect that pyrethroids have on voltage-sensitive calcium channels in general. This information will allow a more complete understanding of the molecular and cellular nature of pyrethroid-induced toxicity and expand our knowledge of the structure-activity relationships of pyrethroids with regard to their action on voltage-sensitive calcium channels.

  15. Exploring the biophysical evidence that mammalian two-pore channels are NAADP-activated calcium-permeable channels.

    Science.gov (United States)

    Pitt, Samantha J; Reilly-O'Donnell, Benedict; Sitsapesan, Rebecca

    2016-08-01

    Nicotinic acid adenine dinucleotide phosphate (NAADP) potently releases Ca(2+) from acidic intracellular endolysosomal Ca(2+) stores. It is widely accepted that two types of two-pore channels, termed TPC1 and TPC2, are responsible for the NAADP-mediated Ca(2+) release but the underlying mechanisms regulating their gating appear to be different. For example, although both TPC1 and TPC2 are activated by NAADP, TPC1 appears to be additionally regulated by cytosolic Ca(2+) . Ion conduction and permeability also differ markedly. TPC1 and TPC2 are permeable to a range of cations although biophysical experiments suggest that TPC2 is slightly more selective for Ca(2+) over K(+) than TPC1 and hence capable of releasing greater quantities of Ca(2+) from acidic stores. TPC1 is also permeable to H(+) and therefore may play a role in regulating lysosomal and cytosolic pH, possibly creating localised acidic domains. The significantly different gating and ion conducting properties of TPC1 and TPC2 suggest that these two ion channels may play complementary physiological roles as Ca(2+) -release channels of the endolysosomal system. PMID:26872338

  16. Optical modulation of neurotransmission using calcium photocurrents through the ion channel LiGluR

    Directory of Open Access Journals (Sweden)

    Mercè eIzquierdo-Serra

    2013-03-01

    Full Text Available A wide range of light-activated molecules (photoswitches and phototriggers have been used to the study of computational properties of an isolated neuron by acting pre and postsynaptically. However, new tools are being pursued to elicit a presynaptic calcium influx that triggers the release of neurotransmitters, most of them based in calcium-permeable Channelrhodopsin-2 mutants. Here we describe a method to control exocytosis of synaptic vesicles through the use of a light-gated glutamate receptor (LiGluR, which has recently been demonstrated that supports secretion by means of calcium influx in chromaffin cells. Expression of LiGluR in hippocampal neurons enables reversible control of neurotransmission with light, and allows modulating the firing rate of the postsynaptic neuron with the wavelength of illumination. This method may be useful for the determination of the complex transfer function of individual synapses.

  17. An integrated multiassay approach to the discovery of small-molecule N-type voltage-gated calcium channel antagonists.

    Science.gov (United States)

    Finley, Michael F A; Lubin, Mary Lou; Neeper, Michael P; Beck, Edward; Liu, Yi; Flores, Christopher M; Qin, Ning

    2010-12-01

    Abstract The N-type voltage-gated calcium channel (Cav2.2) has been intensively explored as a target for novel, small-molecule analgesic drugs because of its distribution in the pain pathway and its role in nociceptive processing. For example, Cav2.2 is localized at presynaptic terminals of pain fibers in the dorsal horn, and it serves as a downstream effector of μ-opioid receptors. Most importantly, antagonism of the channel by the highly specific and potent Cav2.2 blocker ω-conotoxin MVIIA (ziconotide) produces clinical efficacy in the treatment of severe, intractable pain. To identify novel small-molecule Cav2.2 inhibitors, we developed new tools and screening methods critical to enhance the efficiency and probability of success. First, we established and characterized a new cell line stably expressing the three subunits of the Cav2.2, including an α-subunit splice variant that is uniquely expressed by dorsal root ganglion neurons. Second, using this cell line, we validated and employed a fluorescence-based calcium flux assay. Third, we developed a new "medium-throughput" electrophysiology assay using QPatch-HT to provide faster turnaround on high-content electrophysiology data that are critical for studying ion channel targets. Lastly, we used a therapeutically relevant, ex vivo spinal cord calcitonin gene-related peptide-release assay to confirm activities in the other assays. Using this approach we have identified compounds exhibiting single-digit nM IC₅₀ values and with a positive correlation across assay methods. This integrated approach provides a more comprehensive evaluation of small-molecule N-type inhibitors that may lead to improved therapeutic pharmacology. PMID:21050074

  18. Tx1, from Phoneutria nigriventer spider venom, interacts with dihydropyridine sensitive-calcium channels in GH3 cells

    International Nuclear Information System (INIS)

    The aim of this work was to use the binding assay of tritiated-dihydropyridine and radioiodinated Tx1, isolated from the Phoneutria nigriventer venom, in order to show the presence of Cav1 calcium channels on pituitary tumour cell (GH3). We showed that GH3 cells have specific sites for 125I-Tx1, which are sensitive to nifedipine (∼20%). Reverse competition assay with 3H-PN200-110 (40% inhibition) and electrophysiological data (50% inhibition) suggest that Cav1 calcium channels are target sites for this toxin. To summarize, Tx1 binds to specific sites on GH3 cells and this interaction results in Cav1 calcium channel blockade. 3H-PN200-110 and 125I-Tx1 binding assays proved to be useful tools to show the presence of calcium channels on GH3 cells. (author)

  19. Comparison of electrophysiological effects of calcium channel blockers on cardiac repolarization.

    Science.gov (United States)

    Lee, Hyang-Ae; Hyun, Sung-Ae; Park, Sung-Gurl; Kim, Ki-Suk; Kim, Sung Joon

    2016-01-01

    Dihydropyridine (DHP) calcium channel blockers (CCBs) have been widely used to treat of several cardiovascular diseases. An excessive shortening of action potential duration (APD) due to the reduction of Ca(2+) channel current (I Ca) might increase the risk of arrhythmia. In this study we investigated the electrophysiological effects of nicardipine (NIC), isradipine (ISR), and amlodipine (AML) on the cardiac APD in rabbit Purkinje fibers, voltage-gated K(+) channel currents (I Kr, I Ks) and voltage-gated Na(+) channel current (I Na). The concentration-dependent inhibition of Ca(2+) channel currents (I Ca) was examined in rat cardiomyocytes; these CCBs have similar potency on I Ca channel blocking with IC50 (the half-maximum inhibiting concentration) values of 0.142, 0.229, and 0.227 nM on NIC, ISR, and AML, respectively. However, ISR shortened both APD50 and APD90 already at 1 µM whereas NIC and AML shortened APD50 but not APD90 up to 30 µM. According to ion channel studies, NIC and AML concentration-dependently inhibited I Kr and I Ks while ISR had only partial inhibitory effects (NIC and AML could compensate for the AP shortening effects due to the block of I Ca.

  20. The involvement of the Mid1/Cch1/Yvc1 calcium channels in Aspergillus fumigatus virulence.

    Directory of Open Access Journals (Sweden)

    Patrícia Alves de Castro

    Full Text Available Aspergillus fumigatus is a major opportunistic pathogen and allergen of mammals. Calcium homeostasis and signaling is essential for numerous biological processes and also influences A. fumigatus pathogenicity. The presented study characterized the function of the A. fumigatus homologues of three Saccharomyces cerevisiae calcium channels, voltage-gated Cch1, stretch-activated Mid1 and vacuolar Yvc1. The A. fumigatus calcium channels cchA, midA and yvcA were regulated at transcriptional level by increased calcium levels. The YvcA::GFP fusion protein localized to the vacuoles. Both ΔcchA and ΔmidA mutant strains showed reduced radial growth rate in nutrient-poor minimal media. Interestingly, this growth defect in the ΔcchA strain was rescued by the exogenous addition of CaCl2. The ΔcchA, ΔmidA, and ΔcchA ΔmidA strains were also sensitive to the oxidative stress inducer, paraquat. Restriction of external Ca(2+ through the addition of the Ca(2+-chelator EGTA impacted upon the growth of the ΔcchA and ΔmidA strains. All the A. fumigatus ΔcchA, ΔmidA, and ΔyvcA strains demonstrated attenuated virulence in a neutropenic murine model of invasive pulmonary aspergillosis. Infection with the parental strain resulted in a 100% mortality rate at 15 days post-infection, while the mortality rate of the ΔcchA, ΔmidA, and ΔyvcA strains after 15 days post-infection was only 25%. Collectively, this investigation strongly indicates that CchA, MidA, and YvcA play a role in A. fumigatus calcium homeostasis and virulence.

  1. Releasing phosphorus from calcium for struvite fertilizer production from anaerobically digested dairy effluent.

    Science.gov (United States)

    Zhang, Tianxi; Bowers, Keith E; Harrison, Joseph H; Chen, Shulin

    2010-01-01

    Being a non-renewable resource and a source of potential water pollution, phosphorus could be recovered from animal manure in the form of struvite (MgNH4PO4.6H2O) to be used as a slow-release fertilizer. It was found recently that the majority of phosphorus in anaerobically digested dairy effluent is tied up in a fine suspended calcium-phosphate solid, thus becoming unavailable for struvite formation. Acidification and use of a chelating agent were investigated for converting the calcium-associated phosphorus in the digested effluent to dissolved phosphate ions, so that struvite can be produced. The results demonstrated that the phosphorus in the effluent was released into the solution by lowering the pH. In addition, the phosphorus concentration in the solution increased significantly with increased ethylenediaminetetraacetic acid (EDTA) concentration, as EDTA has a high stability constant with calcium. Most of the phosphorus (91%) was released into the solution after adding EDTA. Further, the freed phosphorus ion precipitated out as struvite provided that sufficient magnesium ions (Mg2+) were present in the solution. Furthermore, the phase structure of the solid precipitate obtained from the EDTA treatment matched well with standard struvite, based on the data from X-ray diffraction analysis. These results provide methods for altering the forms of phosphorus for the design and application of phosphorus-removal technologies for dairy wastewater management. PMID:20112536

  2. Effects of coronal leakage on concentration of hydrogen ions and calcium release of several calcium hydroxide pastes over different periods of time

    Directory of Open Access Journals (Sweden)

    Mariana Pires Crespo

    2013-10-01

    Full Text Available PURPOSE: To evaluate the effects of coronal leakage on concentration of hydrogen ions (pH and calcium release of several calcium hydroxide pastes, over different periods of time. MATERIAL AND METHODS:  Fifty extracted human mandibular central incisors (n=10 were instrumented up to the F2 instrument and assigned to the following intracanal dressing: G1- Calen, G2- Calen with 0.4% chlorhexidine (CHX, G3- Calcium hydroxide with camphorated paramonochlorophenol (CPMC and glycerin, G4- Calen, but temporary filling material maintained during all test (positive control and G5- Root canal without intracanal dressing (negative control. All groups were immersed in distilled water for 7 days. In sequence, the temporary filling materials were removed, except in controls groups. All specimens were individually mounted on a specific device and only its root again immersed in distilled water. Concentration of hydrogen ions and calcium release by calcium hydroxide pastes in distilled water were evaluated in 24h, 7, 14 and 28 days. The results were submitted to ANOVA test (p = 0.05. After 28 days, root canals from experimental groups were examined in SEM. RESULTS: G1, G2, G3 and G4 presented similar pH values and calcium release and did not differ from each other (p>0.05, up to 7 days. After this time G1, G2 and G3 presented values lower values than G4 (p<0.05. In SEM analysis, calcium hydroxide residues were observed in all experimental groups. CONCLUSIONS: After 7 days, coronal leakage decreased the concentration of hydrogen ions and calcium ion release provided by all calcium hydroxide pastes.

  3. Mechanism of histamine release from rat mast cells induced by the ionophore A23187: effects of calcium and temperature

    DEFF Research Database (Denmark)

    Johansen, Torben

    1978-01-01

    1 The mechanism of histamine release from a pure population of rat mast cells induced by the lipid soluble antibiotic, A23187, has been studied and compared with data for anaphylactic histamine release reported in the literature. 2 Histamine release induced by A23187 in the presence of calcium 10...

  4. Histamine release induced from rat mast cells by the ionophore A23187 in the absence of extracellular calcium

    DEFF Research Database (Denmark)

    Johansen, Torben

    1980-01-01

    Isolated rat mast cells were used to study whether ionophore A23187 could induce histamine release by mobilizing cellular calcium. The histamine release was a slow process which was completed after about 20 min incubation with A23187. The A23187-induced histamine release was inhibited after...

  5. The BRCA1 Tumor Suppressor Binds to Inositol 1,4,5-Trisphosphate Receptors to Stimulate Apoptotic Calcium Release*

    Science.gov (United States)

    Hedgepeth, Serena C.; Garcia, M. Iveth; Wagner, Larry E.; Rodriguez, Ana M.; Chintapalli, Sree V.; Snyder, Russell R.; Hankins, Gary D. V.; Henderson, Beric R.; Brodie, Kirsty M.; Yule, David I.; van Rossum, Damian B.; Boehning, Darren

    2015-01-01

    The inositol 1,4,5-trisphosphate receptor (IP3R) is a ubiquitously expressed endoplasmic reticulum (ER)-resident calcium channel. Calcium release mediated by IP3Rs influences many signaling pathways, including those regulating apoptosis. IP3R activity is regulated by protein-protein interactions, including binding to proto-oncogenes and tumor suppressors to regulate cell death. Here we show that the IP3R binds to the tumor suppressor BRCA1. BRCA1 binding directly sensitizes the IP3R to its ligand, IP3. BRCA1 is recruited to the ER during apoptosis in an IP3R-dependent manner, and, in addition, a pool of BRCA1 protein is constitutively associated with the ER under non-apoptotic conditions. This is likely mediated by a novel lipid binding activity of the first BRCA1 C terminus domain of BRCA1. These findings provide a mechanistic explanation by which BRCA1 can act as a proapoptotic protein. PMID:25645916

  6. Effects of glycoprotein Ⅱb/Ⅲa antagonists and chloride channel blockers on platelet cytoplasmic free calcium

    Institute of Scientific and Technical Information of China (English)

    YIN Song-mei; XIE Shuang-feng; NIE Da-nian; LI Yi-qing; LI Hai-ming; MA Li-ping; WANG Xiu-ju; WU Yu-dan; FENG Jian-hong

    2005-01-01

    @@ Platelet activation plays an important role in thrombosis. Platelet glycoprotein Ⅱb/Ⅲa (GP Ⅱb/Ⅲa) is the receptor of fibrinogen. Platelet cross-linking with fibrinogen through GPⅡb/Ⅲa is the process of thrombosis. Ca2+ is an important intracellular second messenger in platelet activation. It has been reported that GPⅡb/Ⅲa receptors were involved in the calcium influx of activated platelet, and GPⅡb/Ⅲa receptor had characteristics of calcium channel or an adjacent calcium channel.

  7. Long-Term Blocking of Calcium Channels in mdx Mice Results in Differential Effects on Heart and Skeletal Muscle

    DEFF Research Database (Denmark)

    Jørgensen, Louise Helskov; Blain, Alison; Greally, Elizabeth;

    2011-01-01

    calcium ions to enter the cell. The objective of this study was to investigate the effect of chronically blocking calcium channels with the aminoglycoside antibiotic streptomycin from onset of disease in the mdx mouse model of Duchenne muscular dystrophy (DMD). Treatment in utero onwards delayed onset...... in older mice. However, streptomycin treatment did not show positive effects in diaphragm or heart muscle, and heart pathology was worsened. Thus, blocking calcium channels even before disease onset does not prevent dystrophy, making this an unlikely treatment for DMD. These findings highlight...

  8. Formaldehyde increases intracellular calcium concentration in primary cultured hippocampal neurons partly through NMDA receptors and T-type calcium channels

    Institute of Scientific and Technical Information of China (English)

    Ye-Nan Chi; Xu Zhang; Jie Cai; Feng-Yu Liu; Guo-Gang Xing; You Wan

    2012-01-01

    Objective Formaldehyde at high concentrations is a contributor to air pollution.It is also an endogenous metabolic product in cells,and when beyond physiological concentrations,has pathological effects on neurons.Formaldehyde induces mis-folding and aggregation of neuronal tau protein,hippocampal neuronal apoptosis,cognitive impairment and loss of memory functions,as well as excitation of peripheral nociceptive neurons in cancer pain models.Intracellular calcium ([Ca2+]i) is an important intracellular messenger,and plays a key role in many pathological processes.The present study aimed to investigate the effect of formaldehyde on [Ca2+]i and the possible involvement of N-methyl-D-aspartate receptors (NMDARs) and T-type Ca2+ channels on the cell membrane.Methods Using primary cultured hippocampal neurons as a model,changes of [Ca2+]i in the presence of formaldehyde at a low concentration were detected by confocal laser scanning microscopy.Results Formaldehyde at 1 mmol/L approximately doubled [Ca2+]i.(2R)-amino-5-phosphonopentanoate (AP5,25 μtmol/L,an NMDAR antagonist) and mibefradil (MIB,1 μtmol/L,a T-type Ca2+ channel blocker),given 5 min after formaldehyde perfusion,each partly inhibited the formaldehyde-induced increase of [Ca2+]i,and this inhibitory effect was reinforced by combined application of AP5 and MIB.When applied 3 min before formaldehyde perfusion,AP5 (even at 50 μmol/L) did not inhibit the formaldehyde-induced increase of [Ca2+]i,but MIB (1 μmol/L) significantly inhibited this increase by 70%.Conclusion These results suggest that formaldehyde at a low concentration increases [Ca2+]i in cultured hippocampal neurons; NMDARs and T-type Ca2+ channels may be involved in this process.

  9. Transient receptor potential channel A1 involved in calcitonin gene-related peptide release in neurons

    Institute of Scientific and Technical Information of China (English)

    Nobumasa Ushio; Yi Dai; Shenglan Wang; Tetsuo Fukuoka; Koichi Noguchi

    2013-01-01

    Transient receptor potential channel A1 is one of the important transducers of noxious stimuli in the primary afferents, which may contribute to generation of neurogenic inflammation and hyperalgesia. The present study was designed to investigate if activation of transient receptor potential channel A1 may induce calcitonin gene-related peptide release from the primary afferent neurons. We found that application of al yl isothiocyanate, a transient receptor potential channel A1 activator, caused calcitonin gene-related peptide release from the cultured rat dorsal root ganglion neurons. Knock-down of transient receptor potential channel A1 with an antisense oligodeoxynucleotide prevented calcitonin gene-related peptide release by al yl isothiocyanate application in cultured dorsal root ganglion neurons. Thus, we concluded that transient receptor potential channel A1 activation caused calcitonin gene-related peptide release in sensory neurons.

  10. Solution combustion synthesis of calcium phosphate particles for controlled release of bovine serum albumin

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Junfeng, E-mail: daidai02304@163.com [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China); Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu (China); Zhao, Junjie; Qian, Yu; Zhang, Xiali; Zhou, Feifei; Zhang, Hong [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China); Lu, Hongbin [National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Nanjing University, Nanjing (China); Chen, JianHua; Wang, XuHong [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China); Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu (China); Yu, Wencong [School of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu (China)

    2015-05-01

    Four different phase compositions of calcium phosphate (CaP) particles were prepared via a solution combustion method. X-ray diffraction (XRD) and Rietveld analysis results revealed that the variations in the nominal Ca/P (molar) ratios were found to provide a favorable control in the different proportions of CaP materials. Bovine serum albumin (BSA) was used as a model protein to study the loading and release behavior. The release profile indicated that the BSA release rates depended on the phase compositions of the CaP particles, and showed an order of TCP-BSA > BCP-1-BSA > BCP-2-BSA > HA-BSA. The results suggested that the BSA protein release rate can be controlled by varying the phase compositions of CaP carriers. Moreover, the release process involved two stages: firstly surface diffusion via ion exchange and secondly intraparticle diffusion. - Highlights: • Solution combustion method was an efficient way to produced CaP powders. • Ca/P (molar) ratios provided a favorable control in the different proportions of phase composition. • BSA release rate varied depending on the phase composition of the CaP particles. • Two kinetic models were chosen to simulate the release kinetics of the drugs from CaP carriers.

  11. Calcium Channel Blockers and Esophageal Sclerosis: Should We Expect Exacerbation of Interstitial Lung Disease

    Directory of Open Access Journals (Sweden)

    Charalampos Seretis

    2012-01-01

    Full Text Available Esophageal sclerosis is the most common visceral manifestation of systemic sclerosis, resulting in impaired esophageal clearance and retention of ingested food; in addition, co-existence of lung fibrosis with esophageal scleroderma is not uncommon. Both the progression of generalized connective tissue disorders and the damaging effect of chronic aspiration due to esophageal dysmotility appear to be involved in this procedure of interstitial fibrosis. Nifedipine is a widely prescribed calcium antagonist in a significant percentage of rheumatologic patients suffering from Raynaud syndrome, in order to inhibit peripheral vasospasm. Nevertheless, blocking calcium channels has proven to contribute to exacerbation of gastroesophageal reflux, which consequently can lead to chronic aspiration. We describe the case of severe exacerbation of interstitial lung disease in a 76-year-old female with esophageal sclerosis who was treated with oral nifedipine for Raynaud syndrome.

  12. Antioxidant effect of T-type calcium channel blockers in gastric injury.

    Science.gov (United States)

    Bilici, Dilek; Banoğlu, Z Nur; Kiziltunç, Ahmet; Avci, Bahattin; Ciftçioğlu, Akif; Bilici, Sefa

    2002-04-01

    It is known that calcium ion has an important role in the cellular function. For this reason, calcium channel blockers may have a protective action against gastric injury which is induced by various stimuli. In this study, the influence of mibefradil on ethanol-induced gastric injury was investigated in rats. Mibefradil was given at a dose 50 mg/kg intraperitoneally 30 min before administration of 1 ml absolute ethanol given by gavage. We compared this effect of mibefradil with that of omeprazol. Ethanol-induced mucosal damage was evaluated using three different approaches: analysis of biochemical parameters and pathologic and macroscopic investigation. It was found that pretreatment with mibefradil significantly reduced ethanol-induced macroscopic, pathologic, and biochemical changes in the gastric mucosa. In conclusion, it is speculated that this findings may prove important in the development of new and improved therapies for the treatment and prevention of gastric ulcers in humans. PMID:11991620

  13. Calcium channel blocker prevents stress-induced activation of renin and aldosterone in conscious pig

    International Nuclear Information System (INIS)

    A considerable amount of data suggest the involvement of calcium-mediated processes in the activation of the renin-angiotensin-aldosterone (RAA) cascade. To investigate the effect of calcium-channel inhibition on the RAA system, the authors studied 21 conscious pigs. Blood renin and aldosterone levels increased by subjecting animals to 24 hours of immobilization stress. Renin and aldosterone levels were repeatedly measured by radioimmunoassay in blood samples taken periodically over 24 hours from a chronically implanted arterial cannula. Pretreatment of the animals (N = 11) with nisoldipine, 2 x 20 mg p.o. daily for 2 days before and on the day of immobilization, transiently attenuated the stress-induced increase of plasma renin activity and completely prevented the rise of aldosterone, as compared to nontreated controls (N = 10). The finding that nisoldipine suppresses RAA activation induced by a nonpharmacologic stimulus in the conscious intact animal may have clinical implications

  14. Calcium channel blocker prevents stress-induced activation of renin and aldosterone in conscious pig

    Energy Technology Data Exchange (ETDEWEB)

    Ceremuzynski, L.K.; Klos, J.; Barcikowski, B.; Herbaczynska-Cedro, K. (Department of Cardiology, Postgraduate Medical School, Warsaw (Poland))

    1991-06-01

    A considerable amount of data suggest the involvement of calcium-mediated processes in the activation of the renin-angiotensin-aldosterone (RAA) cascade. To investigate the effect of calcium-channel inhibition on the RAA system, the authors studied 21 conscious pigs. Blood renin and aldosterone levels increased by subjecting animals to 24 hours of immobilization stress. Renin and aldosterone levels were repeatedly measured by radioimmunoassay in blood samples taken periodically over 24 hours from a chronically implanted arterial cannula. Pretreatment of the animals (N = 11) with nisoldipine, 2 {times} 20 mg p.o. daily for 2 days before and on the day of immobilization, transiently attenuated the stress-induced increase of plasma renin activity and completely prevented the rise of aldosterone, as compared to nontreated controls (N = 10). The finding that nisoldipine suppresses RAA activation induced by a nonpharmacologic stimulus in the conscious intact animal may have clinical implications.

  15. Functional importance of T-type voltage-gated calcium channels in the cardiovascular and renal system

    DEFF Research Database (Denmark)

    Hansen, Pernille B L

    2015-01-01

    Over the years, it has been discussed whether T-type calcium channels Cav3 play a role in the cardiovascular and renal system. T-type channels have been reported to play an important role in renal hemodynamics, contractility of resistance vessels, and pacemaker activity in the heart. However, the...

  16. Energetics of discrete selectivity bands and mutation-induced transitions in the calcium-sodium ion channels family

    CERN Document Server

    Kaufman, I; Tindjong, R; McClintock, P V E; Eisenberg, R S

    2013-01-01

    We use Brownian dynamics simulations to study the permeation properties of a generic electrostatic model of a biological ion channel as a function of the fixed charge Q_f at its selectivity filter. We reconcile the recently-discovered discrete calcium conduction bands M0 (Q_f=1e), M1 (3e), M2 (5e) with the set of sodium conduction bands L0 (0.5-0.7e), L1 (1.5-2e) thereby obtaining a completed pattern of conduction and selectivity bands v Q_f for the sodium-calcium channels family. An increase of Q_f leads to an increase of calcium selectivity: L0 (sodium selective, non-blocking channel) -> M0 (non-selective channel) -> L1 (sodium selective channel with divalent block) -> M1 (calcium selective channel exhibiting the anomalous mole fraction effect). We create a consistent identification scheme where the L1 band is identified with the eukaryotic (DEKA) sodium channel, and L0 (speculatively) with the bacterial NaChBac channel. The scheme created is able to account for the experimentally observed mutation-induced ...

  17. Responses of channel catfish (Ictalurus punctatus) swim-up fry to dietary calcium in soft and hard water.

    Science.gov (United States)

    Scarpa, J; Gatlin, D M

    1993-12-01

    1. Responses of channel catfish (Ictalurus punctatus) swim-up fry to dietary calcium in soft ( 100 mg/l as CaCO3) water were determined by feeding purified egg-white diets containing 0, 0.5, 1.0, or 2.0% calcium from CaCO3 for 8 weeks. 2. Catfish fry fed the basal diet (0.03% Ca) in hard and soft water had lower whole-body ash and whole-body calcium concentrations but higher weight gain and survival than those fed calcium-supplemented diets. 3. Fry in soft water generally had lower whole-body ash, whole-body calcium, and survival, as well as a higher incidence of spinal deformities than fry in hard water. 4. Feeding higher levels of calcium to fry reared in soft water did not increase whole-body calcium levels or decrease spinal deformities to the levels observed for fry reared in hard water and fed supplemental calcium. 5. These data indicate that calcium derived solely from dietary or environmental sources was not sufficient for optimum health of channel catfish fry.

  18. Calcium Domains around Single and Clustered IP3 Receptors and Their Modulation by Buffers

    OpenAIRE

    Rüdiger, S; Nagaiah, Ch.; Warnecke, G; J. W. Shuai

    2010-01-01

    We study Ca2+ release through single and clustered IP3 receptor channels on the ER membrane under presence of buffer proteins. Our computational scheme couples reaction-diffusion equations and a Markovian channel model and allows our investigating the effects of buffer proteins on local calcium concentrations and channel gating. We find transient and stationary elevations of calcium concentrations around active channels and show how they determine release amplitude. Transient calcium domains ...

  19. Specific T-type calcium channel isoforms are associated with distinct burst phenotypes in deep cerebellar nuclear neurons

    OpenAIRE

    Molineux, Michael L.; McRory, John E.; McKay, Bruce E.; Hamid, Jawed; Mehaffey, W. Hamish; Rehak, Renata; Snutch, Terrance P; Gerald W Zamponi; Turner, Ray W

    2006-01-01

    T-type calcium channels are thought to transform neuronal output to a burst mode by generating low voltage-activated (LVA) calcium currents and rebound burst discharge. In this study we assess the expression pattern of the three different T-type channel isoforms (Cav3.1, Cav3.2, and Cav3.3) in cerebellar neurons and focus on their potential role in generating LVA spikes and rebound discharge in deep cerebellar nuclear (DCN) neurons. We detected expression of one or more Cav3 channel isoforms ...

  20. New Conotoxin SO-3 Targeting N-type Voltage-Sensitive Calcium Channels

    Directory of Open Access Journals (Sweden)

    Lei Wen

    2006-04-01

    Full Text Available Selective blockers of the N-type voltage-sensitive calcium (CaV channels are useful in the management of severe chronic pain. Here, the structure and function characteristics of a novel N-type CaV channel blocker, SO-3, are reviewed. SO-3 is a 25-amino acid conopeptide originally derived from the venom of Conus striatus, and contains the same 4-loop, 6-cysteine framework (C-C-CC-C-C as O-superfamily conotoxins. The synthetic SO-3 has high analgesic activity similar to ω-conotoxin MVIIA (MVIIA, a selective N-type CaV channel blocker approved in the USA and Europe for the alleviation of persistent pain states. In electrophysiological studies, SO-3 shows more selectivity towards the N-type CaV channels than MVIIA. The dissimilarity between SO-3 and MVIIA in the primary and tertiary structures is further discussed in an attempt to illustrate the difference in selectivity of SO-3 and MVIIA towards N-type CaV channels.

  1. Antischistosomal activity of a calcium channel antagonist on schistosomula and adult Schistosoma mansoni worms

    Directory of Open Access Journals (Sweden)

    Vanessa Silva-Moraes

    2013-08-01

    Full Text Available Current schistosomiasis control strategies are largely based on chemotherapeutic agents and a limited number of drugs are available today. Praziquantel (PZQ is the only drug currently used in schistosomiasis control programs. Unfortunately, this drug shows poor efficacy in patients during the earliest infection phases. The effects of PZQ appear to operate on the voltage-operated Ca2+channels, which are located on the external Schistosoma mansoni membrane. Because some Ca2+channels have dihydropyridine drug class (a class that includes nifedipine sensitivity, an in vitro analysis using a calcium channel antagonist (clinically used for cardiovascular hypertension was performed to determine the antischistosomal effects of nifedipine on schistosomula and adult worm cultures. Nifedipine demonstrated antischistosomal activity against schistosomula and significantly reduced viability at all of the concentrations used alone or in combination with PZQ. In contrast, PZQ did not show significant efficacy when used alone. Adult worms were also affected by nifedipine after a 24 h incubation and exhibited impaired motility, several lesions on the tegument and intense contractility. These data support the idea of Ca2+channels subunits as drug targets and favour alternative therapeutic schemes when drug resistance has been reported. In this paper, strong arguments encouraging drug research are presented, with a focus on exploring schistosomal Ca2+channels.

  2. Shikonin Inhibits Intestinal Calcium-Activated Chloride Channels and Prevents Rotaviral Diarrhea.

    Science.gov (United States)

    Jiang, Yu; Yu, Bo; Yang, Hong; Ma, Tonghui

    2016-01-01

    Secretory diarrhea remains a global health burden and causes major mortality in children. There have been some focuses on antidiarrheal therapies that may reduce fluid losses and intestinal motility in diarrheal diseases. In the present study, we identified shikonin as an inhibitor of TMEM16A chloride channel activity using cell-based fluorescent-quenching assay. The IC50 value of shikonin was 6.5 μM. Short-circuit current measurements demonstrated that shikonin inhibited Eact-induced Cl(-) current in a dose-dependent manner, with IC50 value of 1.5 μM. Short-circuit current measurement showed that shikonin exhibited inhibitory effect against CCh-induced Cl(-) currents in mouse colonic epithelia but did not affect cytoplasmic Ca(2+) concentration as well as the other major enterocyte chloride channel conductance regulator. Characterization study found that shikonin inhibited basolateral K(+) channel activity without affecting Na(+)/K(+)-ATPase activities. In vivo studies revealed that shikonin significantly delayed intestinal motility in mice and reduced stool water content in a neonatal mice model of rotaviral diarrhea without affecting the viral infection process in vivo. Taken together, the results suggested that shikonin inhibited enterocyte calcium-activated chloride channels, the inhibitory effect was partially through inhbition of basolateral K(+) channel activity, and shikonin could be a lead compound in the treatment of rotaviral secretory diarrhea. PMID:27601995

  3. Calmodulin and calcium differentially regulate the neuronal Nav1.1 voltage-dependent sodium channel

    International Nuclear Information System (INIS)

    Highlights: → Both Ca++-Calmodulin (CaM) and Ca++-free CaM bind to the C-terminal region of Nav1.1. → Ca++ and CaM have both opposite and convergent effects on INav1.1. → Ca++-CaM modulates INav1.1 amplitude. → CaM hyperpolarizes the voltage-dependence of activation, and increases the inactivation rate. → Ca++ alone antagonizes CaM for both effects, and depolarizes the voltage-dependence of inactivation. -- Abstract: Mutations in the neuronal Nav1.1 voltage-gated sodium channel are responsible for mild to severe epileptic syndromes. The ubiquitous calcium sensor calmodulin (CaM) bound to rat brain Nav1.1 and to the human Nav1.1 channel expressed by a stably transfected HEK-293 cell line. The C-terminal region of the channel, as a fusion protein or in the yeast two-hybrid system, interacted with CaM via a consensus C-terminal motif, the IQ domain. Patch clamp experiments on HEK1.1 cells showed that CaM overexpression increased peak current in a calcium-dependent way. CaM had no effect on the voltage-dependence of fast inactivation, and accelerated the inactivation kinetics. Elevating Ca++ depolarized the voltage-dependence of fast inactivation and slowed down the fast inactivation kinetics, and for high concentrations this effect competed with the acceleration induced by CaM alone. Similarly, the depolarizing action of calcium antagonized the hyperpolarizing shift of the voltage-dependence of activation due to CaM overexpression. Fluorescence spectroscopy measurements suggested that Ca++ could bind the Nav1.1 C-terminal region with micromolar affinity.

  4. COMPUTER AIDED DESIGN OF SELECTIVE CALCIUM CHANNEL BLOCKERS: USING PHARMACOPHORE - BASED AND DOCKING SIMULATIONS

    Directory of Open Access Journals (Sweden)

    Reetu

    2012-03-01

    Full Text Available In the present study, 3-D QSAR analysis was performed on the previously synthesized and evaluated derivatives of novel 2-arylthiazolidinones as selective analgesic N-type calcium channel blockers. Calcium Channel blockers is the molecular target responsible for the treatment of neuropathic and inflammatory pain. The 3D-QSAR study based on the principle of the alignment of pharmacophoric features by PHASE module of Schrodinger suite has been carried out on the same set of calcium channel blockers. Statistically significant 3-D QSAR model (R2=0.9288 were generated using 21 molecules in the training set. The predictive ability of model was determined using a randomly chosen test set of 6 molecules which gave predictive correlation coefficients (R2pred of 0.946 for 3-D models, indicating good predictive power. PHASE pharmacophore hypothesis AAHR.13 may correspond very closely to the interactions recorded in the active site of the ligand bound complex. These studies produced models with high correlation coefficient and good predictive abilities. Docking studies were also carried out wherein these analogues were docked into the active sites of COX-2 to analyze the receptor-ligand interactions that confer selectivity for COX-2. Compound 2 have the highest dock score (-7.28. In the active site, there are some strong hydrogen-bonding interactions observed between residues GLU67, ALA103, ASP96, SER184 and ASP22. Additionally a correlation of the quantitative structure –activity relationship data and the docking results is found to validate each other and suggest the importance of the binding step in overall drug action.

  5. Structure and selectivity of novel ω-conotoxins and conus catus that target neuronal calcium channel subtypes

    International Nuclear Information System (INIS)

    Full text: ω-Conotoxins selective for N-type voltage-sensitive calcium channels have promising therapeutic applications in conditions such as pain and neurodegeneration following cerebral ischaemia. Here we report the discovery of novel conotoxins from the piscivorous snail Conus carus using 125I-GVIA binding to rat brain membrane to guide fractionation of crude venom, and cloning to identify the expressed gene products from the venom duct tissue. Four peptides were isolated and named ω-conotoxins CVIA-D (CVIA-D) on the basis of their pharmacology and structure. CVIA-D had varying extents of homology to other ω-conotoxins, with loop 4 of CVID showing significant sequence divergence. From binding studies in rat brain, the rank order of potency to displace 125I-GVIA from N-type calcium channel (CVID = GVIA=MVIIA > CVIA > CVIC = CVIB > MVIIC) was reversed at the P/Q-type calcium channel (defined by 125I-MVIIC). CVID was most selective for N-type vs P/Q-type calcium channels, being 1.5 to 2-orders of magnitude more selective than GVIA and MVIIA, respectively. CVIA-D each inhibited neurally-evoked contractions in rat vas deferens in a reversible manner, with potencies that correlated with their ability to inhibit 125I-GVIA binding. Compared with GVIA, CVID was a more potent inhibitor of central N-type calcium channels (α1,B-dexpressed in Xenopus oocytes) than of peripheral N-type calcium channels (rat vas deferens). 1H NMR studies revealed that CVID adopts a similar 3D fold to other ω-conotoxins. However, in contrast to GVIA, MVIIA or MVIIC, CVID has two hydrogen bonds that hold loops 2 and 4 proximal, a factor that may contribute to the enhanced ability of CVID to discriminate among neuronal calcium channels

  6. Synthesis of [3H]FPL 64176, a potent calcium channel activator

    International Nuclear Information System (INIS)

    Tritium labelled FPL 64176 (1, methyl 2,5-dimethyl-4-[2-(phenylmethyl)benzoyl]-1H-pyrrole-3-carboxylate), a potent calcium channel activator with insulinotropic properties was synthesized from the corresponding bromo derivative (3) using tritium gas and Pd/C catalyst. (3) was in turn prepared from methyl 2,5-dimethylpyrrole-3-carboxylate (4) in a one pot procedure. The specific activity of [3H]FPL 64176 was 38 mCi/mmol and radiochemical purity >98%. (Author)

  7. Calcium binding-mediated sustained release of minocycline from hydrophilic multilayer coatings targeting infection and inflammation.

    Directory of Open Access Journals (Sweden)

    Zhiling Zhang

    Full Text Available Infection and inflammation are common complications that seriously affect the functionality and longevity of implanted medical implants. Systemic administration of antibiotics and anti-inflammatory drugs often cannot achieve sufficient local concentration to be effective, and elicits serious side effects. Local delivery of therapeutics from drug-eluting coatings presents a promising solution. However, hydrophobic and thick coatings are commonly used to ensure sufficient drug loading and sustained release, which may limit tissue integration and tissue device communications. A calcium-mediated drug delivery mechanism was developed and characterized in this study. This novel mechanism allows controlled, sustained release of minocycline, an effective antibiotic and anti-inflammatory drug, from nanoscale thin hydrophilic polyelectrolyte multilayers for over 35 days at physiologically relevant concentrations. pH-responsive minocycline release was observed as the chelation between minocycline and Ca(2+ is less stable at acidic pH, enabling 'smart' drug delivery in response to infection and/or inflammation-induced tissue acidosis. The release kinetics of minocycline can be controlled by varying initial loading, Ca(2+ concentration, and Ca(2+ incorporation into different layers, enabling facile development of implant coatings with versatile release kinetics. This drug delivery platform can potentially be used for releasing any drug that has high Ca(2+ binding affinity, enabling its use in a variety of biomedical applications.

  8. Synthesis of porous poly(acrylamide hydrogels using calcium carbonate and its application for slow release of potassium nitrate

    Directory of Open Access Journals (Sweden)

    2009-05-01

    Full Text Available Porous poly(acrylamide was synthesized using calcium carbonate microparticles and subsequent acid treatment to remove the calcium carbonate. Methylenebisacrylamide and ammonium persulfate/sodium metabisulfite were used as crosslinking agent and redox initiator, respectively. The porous structure of resulted hydrogels was confirmed using SEM micrographs. The effect of methylenebisacrylamide concentration and calcium carbonate amount on the swelling of the hydrogels was investigated. The results showed that the effect of methylenebisacrylamide and calcium carbonate variables on the swelling is reverse. The hydrogels were subsequently utilized for the loading of potassium nitrate. Potassium nitrate as active agent was loaded into hydrogels and subsequently the release of this active agent was investigated. In these series of investigation, the effect of content of loading, methylenebisacrylamide and calcium carbonate amount on the release of potassium nitrate from hydrogels was investigated.

  9. 5,6-EET potently inhibits T-type calcium channels

    DEFF Research Database (Denmark)

    Cazade, M.; Bidaud, I.; Hansen, Pernille B. Lærkegaard;

    2014-01-01

    T-type calcium channels (T-channels) are important actors in neuronal pacemaking, in heart rhythm, and in the control of the vascular tone. T-channels are regulated by several endogenous lipids including the primary eicosanoid arachidonic acid (AA), which display an important role in vasodilation...... via its metabolism leading to prostanoids, leukotrienes, and epoxyeicosatrienoic acids (EETs). However, the effects of these latter molecules on T-currents have not been investigated. Here, we describe the effects of the major cyclooxygenase, lipoxygenase, and cytochrome P450 epoxygenase products...... on the three human recombinant T-channels (Ca(v)3.1, Ca(v)3.2, and Ca(v)3.3), as compared to those of AA. We identified the P450 epoxygenase product, 5,6-EET, as a potent physiological inhibitor of Ca(v)3 currents. The effects of 5,6-EET were observed at sub-micromolar concentrations (IC50 = 0.54 mu M...

  10. Mechanism underlying blockade of voltage-gated calcium channels by agmatine in cultured rat hippocampal neurons

    Institute of Scientific and Technical Information of China (English)

    Jian-quan ZHENG; Xie-chuan WENG; Xiao-dan GAI; Jin LI; Wen-bin XIAO

    2004-01-01

    AIM: To investigate whether agmatine could selectively block a given type of the voltage-gated calcium channels (VGCC) and whether related receptors are involved in the blocking effect of agmatine on VGCC. METHODS: The whole-cell patch recording technique was performed to record VGCC currents in the cultured neonatal rat hippocampal neurons. RESULTS: Verapamil (100 μmol/L), a selective blocker of L-type calcium channel, significantly inhibited VGCC current by 80 %± 7 %. Agmatine (100 μmol/L) could further depress the remained currents by 25 %±6 %. The α2-adrenoceptor antagonist yohimbine (10 μmol/L) and the I2 imidazoline receptor antagonist idazoxon (10 and 40 μmol/L) had no significant effect on VGCC currents when used respectively. When the mixture of yohimbine and agmatine was applied, VGCC currents were still depressed remarkably. However, the blocking effect of agmatine was decreased by 29 %± 8 % in the presence of idazoxon (10 μmol/L). The effect of idazoxon did not increase at a higher concentration (40 μmol/L). CONCLUSION: Agmatine could block the L- and other types of VGCC currents in the cultured rat hippocampal neurons. Blocking effect of agmatine on VGCC was partially related to I2 imidazoline receptor and had no relationship with α2-adrenoceptors.

  11. Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans.

    Directory of Open Access Journals (Sweden)

    Shuyuan Liu

    Full Text Available Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers, amlodipine (AML, nifedipine (NIF, benidipine (BEN and flunarizine (FNZ with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1 expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI <0.5, but no interaction against sensitive strains (FICI = 0.56 ~ 2. The mechanism studies revealed that fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin and YVC1 (encoding calcium channel protein in vacuole membrane.

  12. Calcium channels contribute to albiflorin-mediated antinociceptive effects in mouse model.

    Science.gov (United States)

    Zhang, Yizhi; Sun, Dejun; Meng, Qingjin; Guo, Wanxu; Chen, Qiuhui; Zhang, Ying

    2016-08-15

    Albiflorin (AF), one of important bioactive constituents of Paeonia lactiflora Radix, possesses neuro-protective effect. The present study aims to investigate the antinociceptive activities of AF and possible mechanisms. AF suppressed acetic acid-caused writhing, lengthened the latency period of mouse in hot plate test, and reduced the licking and biting response time of the injected mouse paw during phase I and phase II, and it suggested that AF exerted the antinociceptive activity mainly through central nervous system. Nimodipine, a commonly used calcium channels blocker, strongly lengthened AF-enhanced latency period of mouse in hot plate test. Compared with control group, AF reduced the levels of euronal nitric oxide synthase (nNOS), and enhanced the levels of serotonin (5-HT) in serum and/or hypothalamus before and after 30-s thermal stimuli. The reduced activation of calmodulin-dependent protein kinase II and c-Jun N-terminal kinase in hypothalamus was observed in AF-treated mice. Collectively, AF-mediated antinociceptive activities were, at least partially, related to calcium channels. PMID:27038516

  13. Stereoselective inhibition of thromboxane-induced coronary vasoconstriction by 1,4-dihydropyridine calcium channel antagonists

    International Nuclear Information System (INIS)

    The biological activity of the (+)-S- and (-)-R-enantiomers of niguldipine, of the (-)-S- and (+)-R-enantiomers of felodipine and nitrendipine, and of rac-nisoldipine and rac-nimodipine was investigated in vitro and in vivo. Inhibition of coronary vasoconstriction due to the thromboxane A2 (TxA2)-mimetic U-46619 in guinea pig Langendorff hearts, displacement of (+)-[3H]isradipine from calcium channel binding sites of guinea pig skeletal muscle T-tubule membranes, and blood pressure reduction in spontaneously hypertensive rats were determined. The enantiomers were obtained by stereoselective synthesis. Cross-contamination was less than 0.5% for both S- and R-enantiomers of niguldipine and nitrendipine and less than 1% for those of felodipine. From the doses necessary for a 50% inhibition of coronary vasoconstriction, stereoselectivity ratios for (+)-(S)-/(-)-(R)-niguldipine, (-)-(S)-/(+)-(R)-felodipine, and (-)-(S)-/(+)-(R)-nitrendipine of 28, 13, and 7, respectively, were calculated. The potency ratio rac-nisoldipine/rac-nimodipine was 3.5. Ratios obtained from binding experiments and antihypertensive activity were (+)-(S)-/(-)-(R)-niguldipine = 45 and 35, (-)-(S)-/(+)-(R)-felodipine = 12 and 13, (-)-(S)-/(+)-(R)-nitrendipine = 8 and 8, and rac-nisoldipine/rac-nimodipine = 8 and 7, respectively. Highly significant correlations were found between the in vitro potency of the substances to prevent U-46619-induced coronary vasoconstriction and their affinity for calcium channel binding sites as well as their antihypertensive activity

  14. Synergistic Effect of Fluconazole and Calcium Channel Blockers against Resistant Candida albicans.

    Science.gov (United States)

    Liu, Shuyuan; Yue, Longtao; Gu, Wenrui; Li, Xiuyun; Zhang, Liuping; Sun, Shujuan

    2016-01-01

    Candidiasis has increased significantly recently that threatens patients with low immunity. However, the number of antifungal drugs on the market is limited in comparison to the number of available antibacterial drugs. This fact, coupled with the increased frequency of fungal resistance, makes it necessary to develop new therapeutic strategies. Combination drug therapy is one of the most widely used and effective strategy to alleviate this problem. In this paper, we were aimed to evaluate the combined antifungal effects of four CCBs (calcium channel blockers), amlodipine (AML), nifedipine (NIF), benidipine (BEN) and flunarizine (FNZ) with fluconazole against C. albicans by checkerboard and time-killing method. In addition, we determined gene (CCH1, MID1, CNA1, CNB1, YVC1, CDR1, CDR2 and MDR1) expression by quantitative PCR and investigated the efflux pump activity of resistant candida albicans by rhodamine 6G assay to reveal the potential mechanisms. Finally, we concluded that there was a synergy when fluconazole combined with the four tested CCBs against resistant strains, with fractional inhibitory concentration index (FICI) fluconazole plus amlodipine caused down-regulating of CNA1, CNB1 (encoding calcineurin) and YVC1 (encoding calcium channel protein in vacuole membrane).

  15. Calcium-channel blockers and other factors influencing delayed function in renal allografts.

    Science.gov (United States)

    Ferguson, C J; Hillis, A N; Williams, J D; Griffin, P J; Salaman, J R

    1990-01-01

    A retrospective analysis was undertaken to examine the influence of calcium-channel blocking drugs on early renal allograft function. Delayed function was defined as the need for dialysis or a reduction in serum creatinine of less than 15% within 4 days of transplantation. The drug histories of 172 patients were examined. After exclusions, the data from 138 patients were analysed. No patient was taking any calcium-channel blocking drug other than nifedipine. Thirty-one patients were taking nifedipine at the time of transplantation and these had a delayed function rate of 16% compared with 40% for 107 patients not taking nifedipine (chi 2, P less than 0.05). Delayed function occurred in 61% of cases when the donor age was over 50 years compared with 29% with younger donors (chi 2, P less than 0.05). A total ischaemic time of longer than 24 h and administration of inotropic support to the donor were associated with delayed function (chi 2, P less than 0.05). Administration to the donor of mannitol, steroids, phenoxybenzamine and heparin had no effect on the rate of delayed function. Recipients treated with low-dose dopamine in the perioperative period had no advantage. Elevated trough whole blood concentrations of cyclosporin in the first week after transplant were associated with delayed function (Mann-Whitney U, P less than 0.05).

  16. High-dose insulin therapy in beta-blocker and calcium channel-blocker poisoning.

    Science.gov (United States)

    Engebretsen, Kristin M; Kaczmarek, Kathleen M; Morgan, Jenifer; Holger, Joel S

    2011-04-01

    INTRODUCTION. High-dose insulin therapy, along with glucose supplementation, has emerged as an effective treatment for severe beta-blocker and calcium channel-blocker poisoning. We review the experimental data and clinical experience that suggests high-dose insulin is superior to conventional therapies for these poisonings. PRESENTATION AND GENERAL MANAGEMENT. Hypotension, bradycardia, decreased systemic vascular resistance (SVR), and cardiogenic shock are characteristic features of beta-blocker and calcium-channel blocker poisoning. Initial treatment is primarily supportive and includes saline fluid resuscitation which is essential to correct vasodilation and low cardiac filling pressures. Conventional therapies such as atropine, glucagon and calcium often fail to improve hemodynamic status in severely poisoned patients. Catecholamines can increase blood pressure and heart rate, but they also increase SVR which may result in decreases in cardiac output and perfusion of vascular beds. The increased myocardial oxygen demand that results from catecholamines and vasopressors may be deleterious in the setting of hypotension and decreased coronary perfusion. METHODS. The Medline, Embase, Toxnet, and Google Scholar databases were searched for the years 1975-2010 using the terms: high-dose insulin, hyperinsulinemia-euglycemia, beta-blocker, calcium-channel blocker, toxicology, poisoning, antidote, toxin-induced cardiovascular shock, and overdose. In addition, a manual search of the Abstracts of the North American Congress of Clinical Toxicology and the Congress of the European Association of Poisons Centres and Clinical Toxicologists published in Clinical Toxicology for the years 1996-2010 was undertaken. These searches identified 485 articles of which 72 were considered relevant. MECHANISMS OF HIGH-DOSE INSULIN BENEFIT. There are three main mechanisms of benefit: increased inotropy, increased intracellular glucose transport, and vascular dilatation. EFFICACY OF HIGH

  17. Calcium-regulated anion channels in the plasma membrane of Lilium longiflorum pollen protoplasts.

    Science.gov (United States)

    Tavares, Bárbara; Dias, Pedro Nuno; Domingos, Patrícia; Moura, Teresa Fonseca; Feijó, José Alberto; Bicho, Ana

    2011-10-01

    • Currents through anion channels in the plasma membrane of Lilium longiflorum pollen grain protoplasts were studied under conditions of symmetrical anionic concentrations by means of patch-clamp whole-cell configuration. • With Cl(-) -based intra- and extracellular solutions, three outward-rectifying anion conductances, I(Cl1) , I(Cl2) and I(Cl3) , were identified. These three activities were discriminated by differential rundown behaviour and sensitivity to 5-nitro-2-(phenylpropylamino)-benzoate (NPPB), which could not be attributed to one or more channel types. All shared strong outward rectification, activated instantaneously and displayed a slow time-dependent activation for positive potentials. All showed modulation by intracellular calcium ([Ca(2+) ](in) ), increasing intensity from 6.04 nM up to 0.5 mM (I(Cl1) ), or reaching a maximum value with 8.50 μM (I(Cl2) and I(Cl3) ). • After rundown, the anionic currents measured using NO(3) (-) -based solutions were indistinguishable, indicating that the permeabilities of the channels for Cl(-) and NO(3) (-) are similar. Additionally, unitary anionic currents were measured from outside-out excised patches, confirming the presence of individual anionic channels. • This study shows for the first time the presence of a large anionic conductance across the membrane of pollen protoplasts, resulting from the presence of Ca(2+) -regulated channels. A similar conductance was also found in germinated pollen. We hypothesize that these putative channels may be responsible for the large anionic fluxes previously detected by means of self-referencing vibrating probes. PMID:21668885

  18. Vascularization of plastic calcium phosphate cement in vivo induced by in-situ-generated hollow channels.

    Science.gov (United States)

    Yu, Tao; Dong, Chao; Shen, Zhonghua; Chen, Yan; Yu, Bo; Shi, Haishan; Zhou, Changren; Ye, Jiandong

    2016-11-01

    Despite calcium phosphate cement (CPC) is promising for bone repair therapy, slow biodegradation and insufficient vascularization in constructs negatively impacts its clinical application. A self-setting CPC composited with gelatin fiber is investigated to test the utility of this tissue engineering strategy to support rapid and extensive vascularization process. The interconnected hollow channels in CPC are formed after dissolution of gelatin fibers in vivo. The CPC-gelatin samples exhibit relatively decent/enhanced mechanical property, compared to the control. When implanted in vivo, the pre-established vascular networks in material anastomose with host vessels and accelerate vascular infiltration throughout the whole tissue construct. Different channel sizes induce different vascularization behaviors in vivo. Results indicate that the channel with the size of 250μm increases the expression of the representative angiogenic factors HIF1α, PLGF and migration factor CXCR4, which benefit the formation of small vessels. On the other hand, the channel with the size of 500μm enhances VEGF-A expression, which benefit the development of large vessels. Notably, the intersection area of channels has high invasive, sprouting and vasculogenesis potential under hypoxic condition, because more HIF1α-positive cells are observed there. Observation of the CD31-positive lumen in the border of scaffold indicates the ingrowth of blood vessels from its host into material through channel, benefited from gradually increased HIF1α expression. This kind of material was suggested to promote the effective application of bone regeneration through the combination of in situ self-setting, plasticity, angiogenesis, and osteoconductivity. PMID:27524007

  19. Lavender oil-potent anxiolytic properties via modulating voltage dependent calcium channels.

    Directory of Open Access Journals (Sweden)

    Anita M Schuwald

    Full Text Available Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, biochemical, and electrophysiological experiments were investigated in physiological concentrations in the nanomolar range, which correlate to a single dosage of 80 mg/d in humans that was used in clinical trials. We show for the first time that lavender oil bears some similarities with the established anxiolytic pregabalin. Lavender oil inhibits VOCCs in synaptosomes, primary hippocampal neurons and stably overexpressing cell lines in the same range such as pregabalin. Interestingly, Silexan does not primarily bind to P/Q type calcium channels such as pregabalin and does not interact with the binding site of pregabalin, the α2δ subunit of VOCCs. Lavender oil reduces non-selectively the calcium influx through several different types of VOCCs such as the N-type, P/Q-type and T-type VOCCs. In the hippocampus, one brain region important for anxiety disorders, we show that inhibition by lavender oil is mainly mediated via N-type and P/Q-type VOCCs. Taken together, we provide a pharmacological and molecular rationale for the clinical use of the oral application of lavender oil in patients suffering from anxiety.

  20. Changes of neuronal calcium channel following brain damage induced by injection of pertussis bacilli in rats

    Institute of Scientific and Technical Information of China (English)

    陈立华; 于嘉; 刘丽旭; 曹美鸿

    2002-01-01

    To explore changes of neuronal calcium channel following brain damage induced by injection of pertussis bacilli in rats, and to investigate the relationship between cytosolic free calcium concentration ( [ Ca2 + ] i ) in the synaptosome and Ca2 + -ATPase activities of mitochondria. Methods: The level of [ Ca2+ ]i in the synaptosome and Ca2+ -ATPase activities of mitochondria in the acute brain damage induced by injection of pertussis bacilli (PB)in rat was determined and nimodipine was administrated to show its effects on [ Ca2+ ]i in the synaptosome and on alteration of Ca2+ -ATPase activity in the mitochondria.Seventy-three rats were randomly divided into four groups,ie, normal control group (Group A ), sham-operation control group (Group B), PB group (Group C) and nimodipine treatment group (Group D). Results: The level of [ Ca2+ ]i was significantly increased in the PB-injected cerebral hemisphere in the Group C as compared with that in the Group A and the Group B at 30 minutes after injection of PB. The level of [ Ca2+ ]i was kept higher in the 4 hours and 24 hours subgroups after the injection in the Group C ( P < 0.05).In contrast, the Ca2+ -ATPase activities were decreased remarkably among all of the subgroups in the Group C.Nimodipine, which was administered after injection of PB,could significantly decrease the [ Ca2+ ]i and increase the activity of Ca2 + -ATPase ( P < 0.05 ). Conclusions: The neuronal calcium channel is opened after injection of PB. There is a negative correlation between activities of Ca2 +-ATPase and [ Ca2 + ]i.Nimodipine can reduce brain damage through stimulating the activities of Ca2+ -ATPase in the mitochondria, and decrease the level of [ Ca2+ ]i in the synaptosome.Treatment with nimodipine dramatically reduces the effects of brain damage induced by injection of PB.

  1. The effects of S4 segments on the voltage-dependence of inactivation for Cav3.1 calcium channels

    Institute of Scientific and Technical Information of China (English)

    LI JunYing

    2007-01-01

    T-type calcium channels exhibit fast voltage-dependent inactivation,for which the underlying structure-function relationship still remains unclear.To investigate the roles of S4 segments in voltage-dependent inactivation of T-type calcium channels,we created S4 replacement chimeras between Cav3.1 calcium channels(fast voltage-dependent inactivation)and Cav1.2 calcium channels(little oltage-dependent inactivation)by replacing S4s in Cav3.1 with the corresponding regions in Cav1.2.Wild type and chimeric channels were expressed in Xenopus oocytes and channel currents were recorded with two-electrode voltage-clamp.We showed that replacing S4 region in domain I shifted voltage-dependence for inactivation of Cav3.1 to the left,and the V0.5 inact and kinact value were significantly changed.However replacing S4s in domains Ⅱ-Ⅳ had no effects on the voltage-dependent inactivation properties.These results suggest that the roles of S4 segments in domains Ⅰ-Ⅳ are different,and S4 in domain I is likely to be involved in voltage-dependent Inactivation process.Its movement during membrane depolarization may trigger a conformational change in the inactivation gate.

  2. Polychlorinated biphenyl quinone induces endoplasmic reticulum stress, unfolded protein response, and calcium release.

    Science.gov (United States)

    Xu, Demei; Su, Chuanyang; Song, Xiufang; Shi, Qiong; Fu, Juanli; Hu, Lihua; Xia, Xiaomin; Song, Erqun; Song, Yang

    2015-06-15

    Organisms are able to respond to environmental insult to maintain cellular homeostasis, which include the activation of a wide range of cellular adaptive responses with tightly controlled mechanisms. The endoplasmic reticulum (ER) is an organelle responsible for protein folding and calcium storage. ER stress leads to the accumulation of unfolded proteins in the ER lumen. To be against or respond to this effect, cells have a comprehensive signaling system, called unfolded protein response (UPR), to restore homeostasis and normal ER function or activate the cell death program. Therefore, it is critical to understand how environmental insult regulates the ingredients of ER stress and UPR signalings. Previously, we have demonstrated that polychlorinated biphenyl (PCB) quinone caused oxidative stress, cytotoxicity, genotoxicity, and apoptosis in HepG2 cells. Here, we investigated the role of a PCB quinone, PCB29-pQ on ER stress, UPR, and calcium release. PCB29-pQ markedly increased the hallmark genes of ER stress, namely, glucose-regulated protein 78 (GRP78), GRP94, and C/EBP homologous protein (CHOP) on both protein and mRNA levels in HepG2 cells. We also confirmed PCB29-pQ induced ER morphological defects by using transmission electron microscopy. Moreover, PCB29-pQ induced intracellular calcium accumulation and calpain activity, which were significantly inhibited by the pretreatment of BAPTA-AM (Ca(2+) chelator). These results were correlated with the outcome that PCB29-pQ induces ER stress-related apoptosis through caspase family gene 12, while salubrinal and Z-ATAD-FMK (a specific inhibitor of caspase 12) partially ameliorated this effect, respectively. N-Acetyl-l-cysteine (NAC) scavenged ROS formation and consequently alleviated PCB29-pQ-induced expression of ER stress-related genes. In conclusion, our result demonstrated for the first time that PCB quinone leads to ROS-dependent induction of ER stress, and UPR and calcium release in HepG2 cells, and the

  3. Generation of slow wave type action potentials in the mouse small intestine involves a non-L-type calcium channel.

    Science.gov (United States)

    Malysz, J; Richardson, D; Farraway, L; Christen, M O; Huizinga, J D

    1995-10-01

    Intrinsic electrical activities in various isolated segments of the mouse small intestine were recorded (i) to characterize action potential generation and (ii) to obtain a profile on the ion channels involved in initiating the slow wave type action potentials (slow waves). Gradients in slow wave frequency, resting membrane potential, and occurrence of spiking activity were found, with the proximal intestine exhibiting the highest frequency, the most hyperpolarized cell membrane, and the greatest occurrence of spikes. The slow waves were only partially sensitive to L-type calcium channel blockers. Nifedipine, verapamil, and pinaverium bromide abolished spikes that occurred on the plateau phase of the slow waves in all tissues. The activity that remained in the presence of L-type calcium channel blockers, the upstroke potential, retained a similar amplitude to the original slow wave and was of identical frequency. The upstroke potential was not sensitive to a reduction in extracellular chloride or to the sodium channel blockers tetrodotoxin and mexiletine. Abolishment of the Na+ gradient by removal of 120 mM extracellular Na+ reduced the upstroke potential frequency by 13 - 18% and its amplitude by 50 - 70% in the ileum. The amplitude was similarly reduced by Ni2+ (up to 5 mM), and by flufenamic acid (100 mu M), a nonspecific cation and chloride channel blocker. Gadolinium, a nonspecific blocker of cation and stretch-activated channels, had no effect. Throughout these pharmacological manipulations, a robust oscillation remained at 5 - 10 mV. This oscillation likely reflects pacemaker activity. It was rapidly abolished by removal of extracellular calcium but not affected by L-type calcium channel blockers. In summary, the mouse small intestine has been established as a model for research into slow wave generation and electrical pacemaker activity. The upstroke part of the slow wave has two components, the pacemaker component involves a non-L-type calcium channel

  4. Differential neuronal targeting of a new and two known calcium channel β4 subunit splice variants correlates with their regulation of gene expression.

    Science.gov (United States)

    Etemad, Solmaz; Obermair, Gerald J; Bindreither, Daniel; Benedetti, Ariane; Stanika, Ruslan; Di Biase, Valentina; Burtscher, Verena; Koschak, Alexandra; Kofler, Reinhard; Geley, Stephan; Wille, Alexandra; Lusser, Alexandra; Flockerzi, Veit; Flucher, Bernhard E

    2014-01-22

    The β subunits of voltage-gated calcium channels regulate surface expression and gating of CaV1 and CaV2 α1 subunits and thus contribute to neuronal excitability, neurotransmitter release, and calcium-induced gene regulation. In addition, certain β subunits are targeted into the nucleus, where they interact directly with the epigenetic machinery. Whereas their involvement in this multitude of functions is reflected by a great molecular heterogeneity of β isoforms derived from four genes and abundant alternative splicing, little is known about the roles of individual β variants in specific neuronal functions. In the present study, an alternatively spliced β4 subunit lacking the variable N terminus (β4e) is identified. It is highly expressed in mouse cerebellum and cultured cerebellar granule cells (CGCs) and modulates P/Q-type calcium currents in tsA201 cells and CaV2.1 surface expression in neurons. Compared with the other two known full-length β4 variants (β4a and β4b), β4e is most abundantly expressed in the distal axon, but lacks nuclear-targeting properties. To determine the importance of nuclear targeting of β4 subunits for transcriptional regulation, we performed whole-genome expression profiling of CGCs from lethargic (β4-null) mice individually reconstituted with β4a, β4b, and β4e. Notably, the number of genes regulated by each β4 splice variant correlated with the rank order of their nuclear-targeting properties (β4b > β4a > β4e). Together, these findings support isoform-specific functions of β4 splice variants in neurons, with β4b playing a dual role in channel modulation and gene regulation, whereas the newly detected β4e variant serves exclusively in calcium-channel-dependent functions. PMID:24453333

  5. Possible roles of exceptionally conserved residues around the selectivity filters of sodium and calcium channels.

    Science.gov (United States)

    Tikhonov, Denis B; Zhorov, Boris S

    2011-01-28

    In the absence of x-ray structures of sodium and calcium channels their homology models are used to rationalize experimental data and design new experiments. A challenge is to model the outer-pore region that folds differently from potassium channels. Here we report a new model of the outer-pore region of the NaV1.4 channel, which suggests roles of highly conserved residues around the selectivity filter. The model takes from our previous study (Tikhonov, D. B., and Zhorov, B. S. (2005) Biophys. J. 88, 184-197) the general disposition of the P-helices, selectivity filter residues, and the outer carboxylates, but proposes new intra- and inter-domain contacts that support structural stability of the outer pore. Glycine residues downstream from the selectivity filter are proposed to participate in knob-into-hole contacts with the P-helices and S6s. These contacts explain the adapted tetrodotoxin resistance of snakes that feed on toxic prey through valine substitution of isoleucine in the P-helix of repeat IV. Polar residues five positions upstream from the selectivity filter residues form H-bonds with the ascending-limb backbones. Exceptionally conserved tryptophans are engaged in inter-repeat H-bonds to form a ring whose π-electrons would facilitate passage of ions from the outer carboxylates to the selectivity filter. The outer-pore model of CaV1.2 derived from the NaV1.4 model is also stabilized by the ring of exceptionally conservative tryptophans and H-bonds between the P-helices and ascending limbs. In this model, the exceptionally conserved aspartate downstream from the selectivity-filter glutamate in repeat II facilitates passage of calcium ions to the selectivity-filter ring through the tryptophan ring. Available experimental data are discussed in view of the models.

  6. Incorporation of a controlled-release glass into a calcium phosphate cement.

    Science.gov (United States)

    Khairoun, I; Boltong, M G; Gil, F J; Driessens, F C; Planell, J A; Seijas, M M; Martínez, S

    1999-04-01

    A so-called controlled-release glass was synthesized occurring in the system CaO-Na2O-P2O5. A certain sieve fraction of this glass was incorporated in a calcium phosphate cement, of which the powder contained alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate (DCP) and precipitated hydroxyapatite (HA). The glass appeared to retard the cement setting slightly and it reduced considerably the compressive strength after aging in aqueous solutions which were continuously refreshed. Scanning electron microscope (SEM) pictures and X-ray diffraction (XRD) patterns of the samples after 5 weeks of aging showed that the glass was not dissolved but that large brushite crystals were formed. Thereby, aging in CaCl2 solutions resulted in more brushite formation than aging in NaCl solutions. The brushite crystals did not reinforce the cement. Neither was the aged glass-containing cement weaker than it was before the brushite formation right after complete setting. In conclusion, the incorporation of controlled-release glasses into a calcium phosphate cement and subsequent aging in aqueous solutions did not result in the formation of macropores in the cement structure, but that of brushite crystals. This incorporation reduced the compressive strength of the cement considerably.

  7. Effect of Multimodal Pore Channels on Cargo Release from Mesoporous Silica Nanoparticles

    Directory of Open Access Journals (Sweden)

    Sushilkumar A. Jadhav

    2016-01-01

    Full Text Available Mesoporous silica nanoparticles (MSNs with multimodal pore channels were fully characterized by TEM, nitrogen adsorption-desorption, and DLS analyses. MSNs with average diameter of 200 nm with dual pore channel zones with pore diameters of 1.3–2.6 and 4 nm were tested for their use in drug delivery application. Important role of the multimodal pore systems present on MSNs on the quantitative release of model drug ibuprofen was investigated. The results obtained revealed that the release profile for ibuprofen clearly shows distinct zones which can be attributed to the respective porous channel zones present on the particles. The fluctuations in the concentration of ibuprofen during the prolonged release from MSNs were caused by the multimodal pore channel systems.

  8. TRPC1 regulates calcium-activated chloride channels in salivary gland cells.

    Science.gov (United States)

    Sun, Yuyang; Birnbaumer, Lutz; Singh, Brij B

    2015-11-01

    Calcium-activated chloride channel (CaCC) plays an important role in modulating epithelial secretion. It has been suggested that in salivary tissues, sustained fluid secretion is dependent on Ca(2+) influx that activates ion channels such as CaCC to initiate Cl(-) efflux. However direct evidence as well as the molecular identity of the Ca(2+) channel responsible for activating CaCC in salivary tissues is not yet identified. Here we provide evidence that in human salivary cells, an outward rectifying Cl(-) current was activated by increasing [Ca(2+)]i, which was inhibited by the addition of pharmacological agents niflumic acid (NFA), an antagonist of CaCC, or T16Ainh-A01, a specific TMEM16a inhibitor. Addition of thapsigargin (Tg), that induces store-depletion and activates TRPC1-mediated Ca(2+) entry, potentiated the Cl(-) current, which was inhibited by the addition of a non-specific TRPC channel blocker SKF96365 or removal of external Ca(2+). Stimulation with Tg also increased plasma membrane expression of TMEM16a protein, which was also dependent on Ca(2+) entry. Importantly, in salivary cells, TRPC1 silencing, but not that of TRPC3, inhibited CaCC especially upon store depletion. Moreover, primary acinar cells isolated from submandibular gland also showed outward rectifying Cl(-) currents upon increasing [Ca(2+)]i. These Cl(-) currents were again potentiated with the addition of Tg, but inhibited in the presence of T16Ainh-A01. Finally, acinar cells isolated from the submandibular glands of TRPC1 knockout mice showed significant inhibition of the outward Cl(-) currents without decreasing TMEM16a expression. Together the data suggests that Ca(2+) entry via the TRPC1 channels is essential for the activation of CaCC.

  9. Hydrogen ion and calcium releasing of mTA fillapex® and mTA-based formulations

    Directory of Open Access Journals (Sweden)

    Milton Carlos Kuga

    2011-07-01

    Full Text Available Introduction: MTA is composed of various metal oxides, calcium oxide and bismuth. It has good biological properties and is indicated in cases of endodontic complications. Several commercial formulations are available and further studies are necessary to evaluate these materials. Objective: To evaluate pH and calcium releasing of MTA Fillapex® compared with gray and white MTA. Material and methods: Gray and white MTA (Angelus and MTA Fillapex® (Angelus were manipulated and placed into polyethylene tubes and immersed in distilled water. The pH of these solutions was measured at 24 hours, 7 days and 14 days. Simultaneously, at these same aforementioned periods, these materials’ calcium releasing was quantified, through atomic absorption spectrophotometry. The results were submitted to ANOVA, with level of significance at 5%. Results: Concerning to pH, the materials present similar behaviors among each other at 24 hours (p > 0.05. At 7 and 14 days, MTA Fillapex® provided significantly lower pH values than the other materials (p < 0.05. Regarding to calcium releasing, at 24 hours and 7 days, MTA Fillapex® provided lower releasing than the other materials (p < 0.05. After 14 days, differences were found between MTA Fillapex® and gray MTA (p < 0.05. Conclusion: All materials showed alkaline pH and calcium releasing, with significantly lower values for MTA Fillapex® sealer.

  10. A homology model of the pore domain of a voltage-gated calcium channel is consistent with available SCAM data.

    Science.gov (United States)

    Bruhova, Iva; Zhorov, Boris S

    2010-03-01

    In the absence of x-ray structures of calcium channels, their homology models are used to rationalize experimental data and design new experiments. The modeling relies on sequence alignments between calcium and potassium channels. Zhen et al. (2005. J. Gen. Physiol. doi:10.1085/jgp.200509292) used the substituted cysteine accessibility method (SCAM) to identify pore-lining residues in the Ca(v)2.1 channel and concluded that their data are inconsistent with the symmetric architecture of the pore domain and published sequence alignments between calcium and potassium channels. Here, we have built K(v)1.2-based models of the Ca(v)2.1 channel with 2-(trimethylammonium)ethyl methanethiosulfonate (MTSET)-modified engineered cysteines and used Monte Carlo energy minimizations to predict their energetically optimal orientations. We found that depending on the position of an engineered cysteine in S6 and S5 helices, the ammonium group in the long flexible MTSET-modified side chain can orient into the inner pore, an interface between domains (repeats), or an interface between S5 and S6 helices. Different local environments of equivalent positions in the four repeats can lead to different SCAM results. The reported current inhibition by MTSET generally decreases with the predicted distances between the ammonium nitrogen and the pore axis. A possible explanation for outliers of this correlation is suggested. Our calculations rationalize the SCAM data, validate one of several published sequence alignments between calcium and potassium channels, and suggest similar spatial dispositions of S5 and S6 helices in voltage-gated potassium and calcium channels. PMID:20176854

  11. Gynura procumbens Merr. decreases blood pressure in rats by vasodilatation via inhibition of calcium channels

    Directory of Open Access Journals (Sweden)

    See-Ziau Hoe

    2011-01-01

    Full Text Available INTRODUCTION: Gynura procumbens has been shown to decrease blood pressure via inhibition of the angiotensinconverting enzyme. However, other mechanisms that may contribute to the hypotensive effect have not been studied. OBJECTIVES: To investigate the cardiovascular effects of a butanolic fraction of Gynura procumbens in rats. METHODS: Anaesthetized rats were given intravenous bolus injections of butanolic fraction at doses of 2.5-20 mg/kg in vivo. The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro. RESULTS: Intravenous administrations of butanolic fraction elicited significant (p<0.001 and dose-dependent decreases in the mean arterial pressure. However, a significant (p<0.05 decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg. In isolated preparations of rat aortic rings, phenylephrine (1×10-6 M- or potassium chloride (8×10-2 M-precontracted endothelium-intact and -denuded tissue; butanolic fraction (1×10-6-1×10-1 g/ml induced similar concentration-dependent relaxation of the vessels. In the presence of 2.5×10-3 and 5.0×10-3 g/ml butanolic fraction, the contractions induced by phenylephrine (1×10-9-3×10-5 M and potassium chloride (1×10-2-8×10-2 M were significantly antagonized. The calcium-induced vasocontractions (1×10-4-1×10-2 M were antagonized by butanolic fraction concentration-dependently in calcium-free and high potassium (6×10-2 M medium, as well as in calcium- and potassium-free medium containing 1×10-6 M phenylephrine. However, the contractions induced by noradrenaline (1×10-6 M and caffeine (4.5×10-2 M were not affected by butanolic fraction. CONCLUSION: Butanolic fraction contains putative hypotensive compounds that appear to inhibit calcium influx via receptor-operated and/or voltage-dependent calcium channels to cause vasodilation and a consequent fall in blood pressure.

  12. Effects of electromagnetic field exposure on conduction and concentration of voltage gated calcium channels: A Brownian dynamics study.

    Science.gov (United States)

    Tekieh, Tahereh; Sasanpour, Pezhman; Rafii-Tabar, Hashem

    2016-09-01

    A three-dimensional Brownian Dynamics (BD) in combination with electrostatic calculations is employed to specifically study the effects of radiation of high frequency electromagnetic fields on the conduction and concentration profile of calcium ions inside the voltage-gated calcium channels. The electrostatic calculations are performed using COMSOL Multiphysics by considering dielectric interfaces effectively. The simulations are performed for different frequencies and intensities. The simulation results show the variations of conductance, average number of ions and the concentration profiles of ions inside the channels in response to high frequency radiation. The ionic current inside the channel increases in response to high frequency electromagnetic field radiation, and the concentration profiles show that the residency of ions in the channel decreases accordingly. PMID:27346366

  13. Glucocorticoids specifically enhance L-type calcium current amplitude and affect calcium channel subunit expression in the mouse hippocampus.

    NARCIS (Netherlands)

    P.J.P. Chameau; Y.J. Qin; G. Smit; M. Joëls

    2007-01-01

    Previous studies have shown that corticosterone enhances whole cell calcium currents in CA1 pyramidal neurons, through a pathway involving binding of glucocorticoid receptor homodimers to the DNA. We examined whether glucocorticoids show selectivity for L- over N-type of calcium currents. Moreover,

  14. Estradiol coupling to human monocyte nitric oxide release is dependent on intracellular calcium transients: evidence for an estrogen surface receptor.

    Science.gov (United States)

    Stefano, G B; Prevot, V; Beauvillain, J C; Fimiani, C; Welters, I; Cadet, P; Breton, C; Pestel, J; Salzet, M; Bilfinger, T V

    1999-10-01

    We tested the hypothesis that estrogen acutely stimulates constitutive NO synthase (cNOS) activity in human peripheral monocytes by acting on an estrogen surface receptor. NO release was measured in real time with an amperometric probe. 17beta-estradiol exposure to monocytes stimulated NO release within seconds in a concentration-dependent manner, whereas 17alpha-estradiol had no effect. 17beta-estradiol conjugated to BSA (E2-BSA) also stimulated NO release, suggesting mediation by a membrane surface receptor. Tamoxifen, an estrogen receptor inhibitor, antagonized the action of both 17beta-estradiol and E2-BSA, whereas ICI 182,780, a selective inhibitor of the nuclear estrogen receptor, had no effect. We further showed, using a dual emission microfluorometry in a calcium-free medium, that the 17beta-estradiol-stimulated release of monocyte NO was dependent on the initial stimulation of intracellular calcium transients in a tamoxifen-sensitive process. Leeching out the intracellular calcium stores abolished the effect of 17beta-estradiol on NO release. RT-PCR analysis of RNA obtained from the cells revealed a strong estrogen receptor-alpha amplification signal and a weak beta signal. Taken together, a physiological dose of estrogen acutely stimulates NO release from human monocytes via the activation of an estrogen surface receptor that is coupled to increases in intracellular calcium. PMID:10490972

  15. Ions Release and pH of Calcium Hydroxide-, Chlorhexidine- and Bioactive Glass-Based Endodontic Medicaments.

    Science.gov (United States)

    Carvalho, Ceci Nunes; Freire, Laila Gonzales; Carvalho, Alexandre Pinheiro Lima de; Duarte, Marco Antonio Húngaro; Bauer, José; Gavini, Giulio

    2016-01-01

    This study evaluated pH and release of calcium, sodium and phosphate ions from different medications in human dentin. Fifty premolars were prepared and randomly divided into groups: (CHX) - 2% chlorhexidine gel; (CHX + CH) - CHX + calcium hydroxide PA; (CH) - CH + propylene glycol 600; (NPBG) - experimental niobium phosphate bioactive glass + distilled water; (BG) - bioactive glass (Bio-Gran) + distilled water. The specimens were immersed in deionized water and the pH variations were measured. The quantification of ions in the solutions was made by inductively coupled plasma - atomic emission spectroscopy (ICP/AES) at 10 min, 24 h, 7, 14, 21 and 30 days. The results were analyzed by ANOVA and Tukey`s test, with a significance level of 5%. CH had the highest level of calcium ions release at 30 days, while CHX and BG released more sodium ions. BG, NPBG and CHX released a higher amount of phosphate ions. The pH of CH was significantly higher compared with the other groups. CH favored the greatest increase of pH and calcium ions release. The bioactive glasses released more sodium and phosphate ions and presented an alkaline pH immediately and after 30 days. PMID:27224568

  16. Use of clopidogrel and calcium channel blockers and risk of major adverse cardiovascular events

    DEFF Research Database (Denmark)

    Schmidt, Morten; Johansen, Martin B; Robertson, Douglas J;

    2012-01-01

    Eur J Clin Invest 2011 ABSTRACT: Background  The CYP3A4 inhibition by calcium channel blockers (CCBs) may attenuate the effectiveness of clopidogrel. Using time-varying drug exposure ascertainment, we examined whether CCB use modified the association between clopidogrel use and major adverse......-month follow-up, we tracked the use of clopidogrel and CCBs and the rate of MACE (composite of myocardial infarction, ischaemic stroke, stent thrombosis, target lesion revascularization, or cardiac death). We used Cox regression to compute hazard ratios, controlling for potential confounders. Results......  Overall, the 12-month risk for MACE was 14·5%. The rate was 130 per 1000 person years for concomitant clopidogrel and CCB use, 106 for clopidogrel without CCB use, 213 for CCB without clopidogrel use, and 248 for no use of either drug. The adjusted hazard ratio for MACE comparing clopidogrel use...

  17. Development of an 111In-labeled dihydropyridine complex for L-type calcium channel imaging

    International Nuclear Information System (INIS)

    [111In]-DTPA-Amlodipine complex ([111In]-DTPA-AMLO) was prepared starting high purity [111In]indium chloride and conjugated DTPA-AMLO in 30 min at room temperature in acetate buffer in high radiochemical purity (>99 %, RTLC/HPLC; specific activity: 8-10 GBq/mmol). The log P, stability, biodistribution studies and imaging studies in untreated and amlodipine-pretreated rats were determined. The tracer is mostly washed out through kidneys as expected for a dihydropyridine compound. Blocking studies demonstrated high specific binding of the tracer in calcium channel-rich organs including intestine, heart and colon. SPECT images fully supported above results in normal and treated rats. (author)

  18. The mutant Moonwalker TRPC3 channel links calcium signaling to lipid metabolism in the developing cerebellum.

    Science.gov (United States)

    Dulneva, Anna; Lee, Sheena; Oliver, Peter L; Di Gleria, Katalin; Kessler, Benedikt M; Davies, Kay E; Becker, Esther B E

    2015-07-15

    The Moonwalker (Mwk) mouse is a model of dominantly inherited cerebellar ataxia caused by a gain-of-function mutation in the transient receptor potential (TRP) channel TRPC3. Here, we report impairments in dendritic growth and synapse formation early on during Purkinje cell development in the Mwk cerebellum that are accompanied by alterations in calcium signaling. To elucidate the molecular effector pathways that regulate Purkinje cell dendritic arborization downstream of mutant TRPC3, we employed transcriptomic analysis of developing Purkinje cells isolated by laser-capture microdissection. We identified significant gene and protein expression changes in molecules involved in lipid metabolism. Consistently, lipid homeostasis in the Mwk cerebellum was found to be disturbed, and treatment of organotypic cerebellar slices with ceramide significantly improved dendritic outgrowth of Mwk Purkinje cells. These findings provide the first mechanistic insights into the TRPC3-dependent mechanisms, by which activated calcium signaling is coupled to lipid metabolism and the regulation of Purkinje cell development in the Mwk cerebellum.

  19. A key role for STIM1 in store operated calcium channel activation in airway smooth muscle

    Directory of Open Access Journals (Sweden)

    Peel Samantha E

    2006-09-01

    Full Text Available Abstract Background Control of cytosolic calcium plays a key role in airway myocyte function. Changes in intracellular Ca2+ stores can modulate contractile responses, modulate proliferation and regulate synthetic activity. Influx of Ca2+ in non excitable smooth muscle is believed to be predominantly through store operated channels (SOC or receptor operated channels (ROC. Whereas agonists can activate both SOC and ROC in a range of smooth muscle types, the specific trigger for SOC activation is depletion of the sarcoplasmic reticulum Ca2+ stores. The mechanism underlying SOC activation following depletion of intracellular Ca2+ stores in smooth muscle has not been identified. Methods To investigate the roles of the STIM homologues in SOC activation in airway myocytes, specific siRNA sequences were utilised to target and selectively suppress both STIM1 and STIM2. Quantitative real time PCR was employed to assess the efficiency and the specificity of the siRNA mediated knockdown of mRNA. Activation of SOC was investigated by both whole cell patch clamp electrophysiology and a fluorescence based calcium assay. Results Transfection of 20 nM siRNA specific for STIM1 or 2 resulted in robust decreases (>70% of the relevant mRNA. siRNA targeted at STIM1 resulted in a reduction of SOC associated Ca2+ influx in response to store depletion by cyclopiazonic acid (60% or histamine but not bradykinin. siRNA to STIM2 had no effect on these responses. In addition STIM1 suppression resulted in a more or less complete abrogation of SOC associated inward currents assessed by whole cell patch clamp. Conclusion Here we show that STIM1 acts as a key signal for SOC activation following intracellular Ca2+ store depletion or following agonist stimulation with histamine in human airway myocytes. These are the first data demonstrating a role for STIM1 in a physiologically relevant, non-transformed endogenous expression cell model.

  20. The T-type calcium channel antagonist Z944 disrupts prepulse inhibition in both epileptic and non-epileptic rats.

    Science.gov (United States)

    Marks, Wendie N; Greba, Quentin; Cain, Stuart M; Snutch, Terrance P; Howland, John G

    2016-09-22

    The role of T-type calcium channels in brain diseases such as absence epilepsy and neuropathic pain has been studied extensively. However, less is known regarding the involvement of T-type channels in cognition and behavior. Prepulse inhibition (PPI) is a measure of sensorimotor gating which is a basic process whereby the brain filters incoming stimuli to enable appropriate responding in sensory rich environments. The regulation of PPI involves a network of limbic, cortical, striatal, pallidal and pontine brain areas, many of which show high levels of T-type calcium channel expression. Therefore, we tested the effects of blocking T-type calcium channels on PPI with the potent and selective T-type antagonist Z944 (0.3, 1, 3, 10mg/kg; i.p.) in adult Wistar rats and two related strains, the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) and Non-Epileptic Control (NEC). PPI was tested using a protocol that varied prepulse intensity (3, 6, and 12dB above background) and prepulse-pulse interval (30, 50, 80, 140ms). Z944 decreased startle in the Wistar strain at the highest dose relative to lower doses. Z944 dose-dependently disrupted PPI in the Wistar and GAERS strains with the most potent effect observed with the higher doses. These findings suggest that T-type calcium channels contribute to normal patterns of brain activity that regulate PPI. Given that PPI is disrupted in psychiatric disorders, future experiments that test the specific brain regions involved in the regulation of PPI by T-type calcium channels may help inform therapeutic development for those suffering from sensorimotor gating impairments. PMID:27365170

  1. Blockade of L-type calcium channel in myocardium and calcium-induced contractions of vascular smooth muscle by by CPU 86017

    Institute of Scientific and Technical Information of China (English)

    De-zai DAI; Hui-juan HU; Jing ZHAO; Xue-mei HAO; Dong-mei YANG; Pei-ai ZHOU; Cai-hong WU

    2004-01-01

    AIM: To assess the blockade by CPU 86017 on the L-type calcium channels in the myocardium and on the Ca2+related contractions of vascular smooth muscle. METHODS: The whole-cell patch-clamp was applied to investigate the blocking effect of CPU 86017 on the L-type calcium current in isolated guinea pig myocytes and contractions by KC1 or phenylephrine (Phe) of the isolated rat tail arteries were measured. RESULTS: Suppression of the L-type current of the isolated myocytes by CPU 86017 was moderate, in time- and concentration-dependent manner and with no influence on the activation and inactivation curves. The IC50 was 11.5 μmol/L. Suppressive effect of CPU 86017 on vaso-contractions induced by KC1 100 mmol/L, phenylephrine I μmol/Lin KH solution (phase 1),Ca2+ free KH solution ( phase 2), and by addition of CaCI2 into Ca2+-free KH solution (phase 3) were observed. The IC50 to suppress vaso-contractions by calcium entry via the receptor operated channel (ROC) and Voltage-dependent channel (VDC) was 0.324 μmol/L and 16.3 μmol/L, respectively. The relative potency of CPU 86017 to suppress vascular tone by Ca2+ entry through ROC and VDC is 1/187 of prazosin and 1/37 of verapamil, respectively.CONCLUSION: The blocking effects of CPU 86017 on the L-type calcium channel of myocardium and vessel are moderate and non-selective. CPU 86017 is approximately 50 times more potent in inhibiting ROC than VDC.

  2. pH and calcium ion release evaluation of pure and calcium hydroxide-containing Epiphany for use in retrograde filling

    Directory of Open Access Journals (Sweden)

    Mário Tanomaru-Filho

    2011-02-01

    Full Text Available OBJECTIVE: Hydroxyl (OH- and calcium (Ca++ ion release was evaluated in six materials: G1 Sealer 26, G2 White mineral trioxide aggregate (MTA, G3 Epiphany, G4 Epiphany + 10% calcium hydroxide (CH, G5 Epiphany + 20% CH, and G6 zinc oxide and eugenol. MATERIAL AND METHODS: Specimens were placed in polyethylene tubes and immersed in distilled water. After 3, 6, 12, 24, and 48 h, 7, 14, and 28 days, the water was assessed for pH with a pH meter and for Ca++ release by atomic absorption spectrophotometry. RESULTS: G1, G2, G4, and G5 had the highest pH until 14 days (p<0.05. G1 presented the highest Ca++ release until 6 h, and G4 and G5, from 12 h through 14 days. Ca++ release was greater for G1 and G2 at 28 days. G6 released the least Ca++. CONCLUSIONS: MTA, Sealer 26, Epiphany, and Epiphany + CH release OH- and Ca++ ions. Epiphany + CH may be an alternative as retrofilling material.

  3. TRPV4 and AQP4 Channels Synergistically Regulate Cell Volume and Calcium Homeostasis in Retinal Müller Glia

    DEFF Research Database (Denmark)

    Jo, Andrew O; Ryskamp, Daniel A; Phuong, Tam T T;

    2015-01-01

    through TRPV4 channels reciprocally modulates volume regulation, swelling, and Aqp4 gene expression. Therefore, TRPV4-AQP4 interactions constitute a molecular system that fine-tunes astroglial volume regulation by integrating osmosensing, calcium signaling, and water transport and, when overactivated...

  4. The L-Type Calcium Channel Blocker Nifedipine Impairs Extinction, but Not Reduced Contingency Effects, in Mice

    Science.gov (United States)

    Jami, Shekib; Barad, Mark; Cain, Christopher K.; Godsil, Bill P.

    2005-01-01

    We recently reported that fear extinction, a form of inhibitory learning, is selectively blocked by systemic administration of L-type voltage-gated calcium channel (LVGCC) antagonists, including nifedipine, in mice. We here replicate this finding and examine three reduced contingency effects after vehicle or nifedipine (40 mg/kg) administration.…

  5. Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels

    DEFF Research Database (Denmark)

    Hansen, P B L

    2013-01-01

    -type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular...

  6. Efficacy and safety of calcium channel blockers in heart failure : Focus on recent trials with second-generation dihydropyridines

    NARCIS (Netherlands)

    de Vries, RJM; van Veldhuisen, DJ; Dunselman, PHJM

    2000-01-01

    Background Chronic heart failure (CHF) has high morbidity and mortality rates despite treatment with angiotensin-converting-enzyme inhibitors, diuretics, and digoxin. Adjunctive-vasodilation through calcium channel blockade has been suggested as potentially useful, However, the first-generation calc

  7. L—type calcium channel blockers inhibit the development but not the expression of sensitization to morphine in mice

    Institute of Scientific and Technical Information of China (English)

    ZhanQ; ZhenJW

    2002-01-01

    The relationship between opioid actions and L-type calcium channel blockers has been well documented.However,there is no report relevant to L-type calcium channel blockers and morphinesensitization,which is suggested to be an analog of behaviors that are the characteristics of drug addiction.Here the effects of three L-type calcium channel blockers,nimodipine,nifedipine and verapamil,on morphine-induced locomotor activity,the development and the expression of sensitization to morphine were studied systematically.The results showed that both nimodipine and verapamil attenuated,while nifedipine had only a tendency to decrease morphine-induced locomotor activity.All the three drugs inhibited the development of sensitization to morphine.However,none of them showed any effects on the expression of morphine sensitization.These results indicate that blocking L-tpye calcium channel attenuates the locomotor stimulating effects of morphine and inhibits the development but not the expression of morphine-sensitization.

  8. Dopamine Induces LTP Differentially in Apical and Basal Dendrites through BDNF and Voltage-Dependent Calcium Channels

    Science.gov (United States)

    Navakkode, Sheeja; Sajikumar, Sreedharan; Korte, Martin; Soong, Tuck Wah

    2012-01-01

    The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC).…

  9. Caffeine Alters Skeletal Muscle Contraction by Opening of Calcium Ion Channels

    Directory of Open Access Journals (Sweden)

    Kolawole Victor Olorunshola

    2011-09-01

    Full Text Available The aim of this study was to investigate the effect of caffeine on the amplitude and rate of skeletal muscle contraction using frog sciatic nerve-gastrocnemius muscle model. Caffeine is a xanthine alkaloid whose use is widely unregulated. It is taken as a central nervous system stimulant in various foods and drinks. The effect of caffeine on skeletal muscle contraction and a possible elucidation of its mechanism of action were investigated. The sciatic nerve-gastrocnemius muscle preparation of the frog mounted on a kymograph was utilized. Varying doses of caffeine was added to the organ bath at 5, 10, 15, 20 and 25 mg/mL and its effect on skeletal muscle contraction was studied. The effects of caffeine preceded by administration of acetylcholine, atropine, nifedipine, magnesium chloride and calcium gluconate at 25 mg/mL were also studied. A dose dependent increase in skeletal muscle contraction (25.25±0.48, 49.00±1.23, 52.38±2.58, 59.25±1.11 and 68.50±0.87 mV; p<0.05 was observed on administration of increasing doses (5, 10, 15, 20 and 25 mg/mL, respectively of caffeine respectively. While a significant reduction (0.90±0.04 mV and increase (77.50±1.56 mV in strength of contraction was observed on administration of nifedipine and calcium gluconate respectively. Administration of magnesium chloride caused a significant decrease in the strength of contraction (28.25±5.01 as compared to control. However, there was no significant difference in the contraction period and relaxation period between the treatment groups. The findings imply that caffeine increases skeletal muscle contraction and suggests it exerts the effect through increasing calcium ion release.

  10. Differential expression of T- and L-type voltage-dependent calcium channels in renal resistance vessels

    DEFF Research Database (Denmark)

    Hansen, Pernille B. Lærkegaard; Jensen, Boye L.; Andreasen, D;

    2001-01-01

    The distribution of voltage-dependent calcium channels in kidney pre- and postglomerular resistance vessels was determined at the molecular and functional levels. Reverse transcription-polymerase chain reaction analysis of microdissected rat preglomerular vessels and cultured smooth muscle cells...... showed coexpression of mRNAs for T-type subunits (Ca(V)3.1, Ca(V)3.2) and for an L-type subunit (Ca(V)1.2). The same expression pattern was observed in juxtamedullary efferent arterioles and outer medullary vasa recta. No calcium channel messages were detected in cortical efferent arterioles. Ca(V)1.......2 protein was demonstrated by immunochemical labeling of rat preglomerular vasculature and juxtamedullary efferent arterioles and vasa recta. Cortical efferent arterioles were not immunopositive. Recordings of intracellular calcium concentration with digital fluorescence imaging microscopy showed a...

  11. Modulated Hawking radiation and a nonviolent channel for information release

    Directory of Open Access Journals (Sweden)

    Steven B. Giddings

    2014-11-01

    Full Text Available Unitarization of black hole evaporation requires that quantum information escapes a black hole; an important question is to identify the mechanism or channel by which it does so. Accurate counting of black hole states via the Bekenstein–Hawking entropy would indicate this information should be encoded in radiation with average energy flux matching Hawking's. Information can be encoded with no change in net flux via fine-grained modulation of the Hawking radiation. In an approximate effective field theory description, couplings to the stress tensor of the black hole atmosphere that depend on the internal state of the black hole are a promising alternative for inducing such modulation. These can be picturesquely thought of as due to state-dependent metric fluctuations in the vicinity of the horizon. Such couplings offer the prospect of emitting information without extra energy flux, and can be shown to do so at linear order in the couplings, with motivation given for possible extension of this result to higher orders. The potential advantages of such couplings to the stress tensor thus extend beyond their universality, which is helpful in addressing constraints from black hole mining.

  12. Experimental evidence for cadmium uptake via calcium channels in the aquatic insect Chironomus staegeri

    International Nuclear Information System (INIS)

    We used the chironomid Chironomus staegeri to investigate the mechanism of cadmium (Cd) uptake in aquatic insects. We exposed C. staegeri larvae to a low nominal Cd concentration (50 nM) for 3 days and measured the effects of calcium (Ca) concentration (0.1-10 mM Ca) as well as the Ca channel blockers lanthanum and verapamil on Cd accumulation. When Ca2+ concentrations were increased above a control (0.1 mM Ca2+) to 1-10 mM, Cd accumulation by larvae was inhibited by from 46 to 88%, respectively. A simple theoretical model of Cd-Ca competition for uptake sites fitted our observations well. Cadmium accumulation was significantly inhibited in a concentration-dependent manner by both La (73% at 10 μM and 92% at 100 μM) and verapamil (59% at 100 μM and 85% at 300 μM). Our findings represent strong evidence that Cd entry into these insects occurs through Ca channels. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  13. Inhibition of nitrite-induced toxicity in channel catfish by calcium chloride and sodium chloride

    Science.gov (United States)

    Tommasso J.R., Wright; Simco, B.A.; Davis, K.B.

    1980-01-01

    Environmental chloride has been shown to inhibit methemoglobin formation in fish, thereby offering a protective effect against nitrite toxicity. Channel catfish (Ictalurus punctatus) were simultaneously exposed to various environmental nitrite and chloride levels (as either CaCl2 or NaCl) in dechlorinated tap water (40 mg/L total hardness, 47 mg/L alkalinity, 4 mg/L chloride, pH = 6.9-7.1, and temperature 21-24°C). Methemoglobin levels in fish simultaneously exposed to 2.5 mg/L nitrite and up to 30 mg/L chloride as either CaCl2 or NaCl were similar but significantly lower than in unprotected fish. Exposure to 10 mg/L nitrite and 60 mg/L chloride resulted in methemoglobin levels similar to those of the controls; most unprotected fish died. Fish exposed to 10 mg/L nitrite had significantly lower methemoglobin levels when protected with 15.0 mg/L chloride as CaCl2 than with NaCl. Fish exposed to nitrite in the presence of 60 mg/L chloride (as either CaCl2 or NaCl) had similar 24-h LC50 values that were significantly elevated above those obtained in the absence of chloride. Calcium had little effect on tolerance to nitrite toxicity in channel catfish in contrast to its large effect reported in steelhead trout (Salmo gairdneri).

  14. On the burnout in annular channels at non-uniform heat release distribution in length

    International Nuclear Information System (INIS)

    The effect of axial heat release non-uniformity on the conditions of the burnout in annular channels is investigated. The investigation is carried out in annular channels with different laws of heat flux density distribution by channel length. The heat release non-uniformity coefficient was varied from 4.4 to 10, the pressure from 9.8 to 17.6 MPa, mass rate from 500 to 1700 kg (m2xS), liquid temperature (chemically desalted water) at the channel inlet constituted 30-300 deg C. The experiments have been performed at the test bench with a closed circulation circuit. The data obtained testify to the fact that under non-uniform heat release the influence of main operating parameters on the value of critical power is of the same character as under uniform heat release. The character of wall temperature variation by channel length before the burnout is determined by the form of heat supply temperature profile. The temperature maximum is observed in the region lying behind the cross section with maximum heat flux. The conclusion is drawn that the dominant influence on the position of the cross section in which the burnout arises is exerted by the form of heat flux density distribution by length. Independently of this distribution form the burnout developes when the vapour content near the wall reaches a limiting value

  15. Calcium-dependent modulation and plasma membrane targeting of the AKT2 potassium channel by the CBL4/ CIPK6 calcium sensor/protein kinase complex

    Institute of Scientific and Technical Information of China (English)

    Katrin Held; Jean-Baptiste Thibaud; J(o)rg Kudla; Francois Pascaud; Christian Eckert; Pawel Gajdanowicz; Kenji Hashimoto; Claire Corratgé-Faillie; Jan Niklas Offenborn; Beno(i)t Lacombe; Ingo Dreyer

    2011-01-01

    Potassium (K+) channel function is fundamental to many physiological processes. However, components and mechanisms regulating the activity of plant K+ channels remain poorly understood. Here, we show that the calcium (Ca2+)sensor CBL4 together with the interacting protein kinase CIPK6 modulates the activity and plasma membrane (PM)targeting of the K+ channel AKT2 from Arabidopsis thaliana by mediating translocation of AKT2 to the PM in plant cells and enhancing AKT2 activity in oocytes. Accordingly, akt2, cbl4 and cipk6 mutants share similar developmental and delayed flowering pheuotypes. Moreover, the isolated regulatory C-terminal domain of CIPK6 is sufficient for mediating CBL4- and Ca2+-dependent channel translocation from the endoplasmic reticulum membrane to the PM by a novel targeting pathway that is dependent on dual lipid modifications of CBL4 by myristoylation and palmitoylation. Thus, we describe a critical mechanism of ion-channel regulation where a Ca2+ sensor modulates K+ channel activity by promoting a kinase interaction-dependent but phosphorylation-independent translocation of the channel to the PM.

  16. The calcium channel β2 (CACNB2 subunit repertoire in teleosts

    Directory of Open Access Journals (Sweden)

    Mueller Rachel

    2008-04-01

    Full Text Available Abstract Background Cardiomyocyte contraction is initiated by influx of extracellular calcium through voltage-gated calcium channels. These oligomeric channels utilize auxiliary β subunits to chaperone the pore-forming α subunit to the plasma membrane, and to modulate channel electrophysiology 1. Several β subunit family members are detected by RT-PCR in the embryonic heart. Null mutations in mouse β2, but not in the other three β family members, are embryonic lethal at E10.5 due to defects in cardiac contractility 2. However, a drawback of the mouse model is that embryonic heart rhythm is difficult to study in live embryos due to their intra-uterine development. Moreover, phenotypes may be obscured by secondary effects of hypoxia. As a first step towards developing a model for contributions of β subunits to the onset of embryonic heart rhythm, we characterized the structure and expression of β2 subunits in zebrafish and other teleosts. Results Cloning of two zebrafish β2 subunit genes (β2.1 and β2.2 indicated they are membrane-associated guanylate kinase (MAGUK-family genes. Zebrafish β2 genes show high conservation with mammals within the SH3 and guanylate kinase domains that comprise the "core" of MAGUK proteins, but β2.2 is much more divergent in sequence than β2.1. Alternative splicing occurs at the N-terminus and within the internal HOOK domain. In both β2 genes, alternative short ATG-containing first exons are separated by some of the largest introns in the genome, suggesting that individual transcript variants could be subject to independent cis-regulatory control. In the Tetraodon nigrovidis and Fugu rubripes genomes, we identified single β2 subunit gene loci. Comparative analysis of the teleost and human β2 loci indicates that the short 5' exon sequences are highly conserved. A subset of 5' exons appear to be unique to teleost genomes, while others are shared with mammals. Alternative splicing is temporally and

  17. RGS12 interacts with the SNARE-binding region of the Cav2.2 calcium channel.

    Science.gov (United States)

    Richman, Ryan W; Strock, Jesse; Hains, Melinda D; Cabanilla, Nory Jun; Lau, King-Kei; Siderovski, David P; Diversé-Pierluissi, María

    2005-01-14

    Activation of GABAB receptors in chick dorsal root ganglion (DRG) neurons inhibits the Cav2.2 calcium channel in both a voltage-dependent and voltage-independent manner. The voltage-independent inhibition requires activation of a tyrosine kinase that phosphorylates the alpha1 subunit of the channel and thereby recruits RGS12, a member of the "regulator of G protein signaling" (RGS) proteins. Here we report that RGS12 binds to the SNARE-binding or "synprint" region (amino acids 726-985) in loop II-III of the calcium channel alpha1 subunit. A recombinant protein encompassing the N-terminal PTB domain of RGS12 binds to the synprint region in protein overlay and surface plasmon resonance binding assays; this interaction is dependent on tyrosine phosphorylation and yet is within a sequence that differs from the canonical NPXY motif targeted by other PTB domains. In electrophysiological experiments, microinjection of DRG neurons with synprint-derived peptides containing the tyrosine residue Tyr-804 altered the rate of desensitization of neurotransmitter-mediated inhibition of the Cav2.2 calcium channel, whereas peptides centered about a second tyrosine residue, Tyr-815, were without effect. RGS12 from a DRG neuron lysate was precipitated using synprint peptides containing phosphorylated Tyr-804. The high degree of conservation of Tyr-804 in the SNARE-binding region of Cav2.1 and Cav2.2 calcium channels suggests that this region, in addition to the binding of SNARE proteins, is also important for determining the time course of the modulation of calcium current via tyrosine phosphorylation.

  18. Stochastic models of intracellular calcium signals

    International Nuclear Information System (INIS)

    Cellular signaling operates in a noisy environment shaped by low molecular concentrations and cellular heterogeneity. For calcium release through intracellular channels–one of the most important cellular signaling mechanisms–feedback by liberated calcium endows fluctuations with critical functions in signal generation and formation. In this review it is first described, under which general conditions the environment makes stochasticity relevant, and which conditions allow approximating or deterministic equations. This analysis provides a framework, in which one can deduce an efficient hybrid description combining stochastic and deterministic evolution laws. Within the hybrid approach, Markov chains model gating of channels, while the concentrations of calcium and calcium binding molecules (buffers) are described by reaction–diffusion equations. The article further focuses on the spatial representation of subcellular calcium domains related to intracellular calcium channels. It presents analysis for single channels and clusters of channels and reviews the effects of buffers on the calcium release. For clustered channels, we discuss the application and validity of coarse-graining as well as approaches based on continuous gating variables (Fokker–Planck and chemical Langevin equations). Comparison with recent experiments substantiates the stochastic and spatial approach, identifies minimal requirements for a realistic modeling, and facilitates an understanding of collective channel behavior. At the end of the review, implications of stochastic and local modeling for the generation and properties of cell-wide release and the integration of calcium dynamics into cellular signaling models are discussed

  19. Stochastic models of intracellular calcium signals

    Energy Technology Data Exchange (ETDEWEB)

    Rüdiger, Sten, E-mail: sten.ruediger@physik.hu-berlin.de

    2014-01-10

    Cellular signaling operates in a noisy environment shaped by low molecular concentrations and cellular heterogeneity. For calcium release through intracellular channels–one of the most important cellular signaling mechanisms–feedback by liberated calcium endows fluctuations with critical functions in signal generation and formation. In this review it is first described, under which general conditions the environment makes stochasticity relevant, and which conditions allow approximating or deterministic equations. This analysis provides a framework, in which one can deduce an efficient hybrid description combining stochastic and deterministic evolution laws. Within the hybrid approach, Markov chains model gating of channels, while the concentrations of calcium and calcium binding molecules (buffers) are described by reaction–diffusion equations. The article further focuses on the spatial representation of subcellular calcium domains related to intracellular calcium channels. It presents analysis for single channels and clusters of channels and reviews the effects of buffers on the calcium release. For clustered channels, we discuss the application and validity of coarse-graining as well as approaches based on continuous gating variables (Fokker–Planck and chemical Langevin equations). Comparison with recent experiments substantiates the stochastic and spatial approach, identifies minimal requirements for a realistic modeling, and facilitates an understanding of collective channel behavior. At the end of the review, implications of stochastic and local modeling for the generation and properties of cell-wide release and the integration of calcium dynamics into cellular signaling models are discussed.

  20. Water Channels Are Involved in Stomatal Oscillations Encoded by Parameter-Specific Cytosolic Calcium Oscillations

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Earlier studies have shown that various stimuli can induce specific cytosolic calcium ([Ca2+]cyt) oscillations in guard cells and various oscillations in stomatal apertures. Exactly how [Ca2+]cyt oscillation signaling functions in stomatal oscillation is not known. In the present study, the epidermis of broad bean (Vicia faba L.)was used and a rapid ion-exchange treatment with two shifting buffers differing in K+ and Ca2+ concentrations was applied. The treatment for five transients at a 10-min transient period induced clear and regular stomatal oscillation. However, for other transient numbers and periods, the treatments induced some irregular oscillations or even no obvious oscillations in stomatal aperture. The results indicate that stomatal oscillation is encoded by parameter-specific [Ca2+]cyt oscillation: the parameters of [Ca2+]cyt oscillation affected the occurrence rate and the parameters of stomatal oscillation. The water channel inhibitor HgCl2 completely inhibited stomatal oscillation and the inhibitory effect could be partially reversed by β-mercaptoethanol (an agent capable of reversing water channel inhibition by HgCl2). Other inhibitory treatments against ion transport (i.e. the application of LaCl3, EGTA, or tetraethylammonium chloride (TEACl))weakly impaired stomatal oscillation when the compounds were added after rapid ion-exchange treatment.If these compounds were added before rapid-ion exchange treatment, the inhibitory effect was much more apparent (except in the case of TEACI). The results of the present study suggest that water channels are involved in stomatal oscillation as a downstream element of [Ca2+]cyt oscillation signaling.

  1. Modeling within- and across-channel processes in comodulation masking release

    DEFF Research Database (Denmark)

    Dau, Torsten; Piechowiak, Tobias; Ewert, Stephan D

    2013-01-01

    The relative contributions of within-channel and across-channel processes to perceptual comodulation masking release (CMR) were investigated in the framework of an auditory processing model. A generalized version of the computational auditory signal processing and perception model [CASP; Jepsen et...... al., J. Acoust. Soc. Am. 124, 422-438 (2008)] was used and extended by an across-channel modulation processing stage according to Piechowiak et al. [J. Acoust. Soc. Am. 121, 2111-2126 (2007)]. Five experimental paradigms were considered: CMR with a broadband noise masker as a function of the masker...... different mechanisms contribute to overall CMR in the considered conditions: (1) a within-channel process based on changes in the envelope characteristic due to the addition of the signal to the masker; (2) a within-channel process based on nonlinear peripheral processing of the OFB's envelope caused...

  2. Calcium-sensing receptor activation contributed to apoptosis stimulates TRPC6 channel in rat neonatal ventricular myocytes

    International Nuclear Information System (INIS)

    Capacitative calcium entry (CCE) refers to the influx of calcium through plasma membrane channels activated on depletion of endoplasmic sarcoplasmic/reticulum (ER/SR) Ca2+ stores, which is performed mainly by the transient receptor potential (TRP) channels. TRP channels are expressed in cardiomyocytes. Calcium-sensing receptor (CaR) is also expressed in rat cardiac tissue and plays an important role in mediating cardiomyocyte apoptosis. However, there are no data regarding the link between CaR and TRP channels in rat heart. In this study, in rat neonatal myocytes, by Ca2+ imaging, we found that the depletion of ER/SR Ca2+ stores by thapsigargin (TG) elicited a transient rise in cytoplasmic Ca2+ ([Ca2+]i), followed by sustained increase depending on extracellular Ca2+. But, TRP channels inhibitor (SKF96365), not L-type channels or the Na+/Ca2+ exchanger inhibitors, inhibited [Ca2+]i relatively high. Then, we found that the stimulation of CaR with its activator gadolinium chloride (GdCl3) or by an increased extracellular Ca2+([Ca2+]o) increased the concentration of intracelluar Ca2+, whereas, the sustained elevation of [Ca2+]i was reduced in the presence of SKF96365. Similarly, the duration of [Ca2+]i increase was also shortened in the absence of extracellular Ca2+. Western blot analysis showed that GdCl3 increased the expression of TRPC6, which was reversed by SKF96365. Additionally, SKF96365 reduced cardiomyocyte apoptosis induced by GdCl3. Our results suggested that CCE exhibited in rat neonatal myocytes and CaR activation induced Ca2+-permeable cationic channels TRPCs to gate the CCE, for which TRPC6 was one of the most likely candidates. TRPC6 channel was functionally coupled with CaR to enhance the cardiomyocyte apoptosis.

  3. A cell model study of calcium influx mechanism regulated by calcium-dependent potassium channels in Purkinje cell dendrites.

    Science.gov (United States)

    Chono, Koji; Takagi, Hiroshi; Koyama, Shozo; Suzuki, Hideo; Ito, Etsuro

    2003-10-30

    The present study was designed to elucidate the roles of dendritic voltage-gated K+ channels in Ca2+ influx mechanism of a rat Purkinje cell using a computer simulation program. First, we improved the channel descriptions and the maximum conductance in the Purkinje cell model to mimic both the kinetics of ion channels and the Ca2+ spikes, which had failed in previous studies. Our cell model is, therefore, much more authentic than those in previous studies. Second, synaptic inputs that mimic stimulation of parallel fibers and induce sub-threshold excitability were simultaneously applied to the spiny dendrites. As a result, transient Ca2+ responses were observed in the stimulation points and they decreased with the faster decay rate in the cell model including high-threshold Ca2+-dependent K+ channels than in those excluding these channels. Third, when a single synaptic input was applied into a spiny dendrite, Ca2+-dependent K+ channels suppressed Ca2+ increases at stimulation and recording points. Finally, Ca2+-dependent K+ channels were also found to suppress the time to peak Ca2+ values in the recording points. These results suggest that the opening of Ca2+-dependent K+ channels by Ca2+ influx through voltage-gated Ca2+ channels hyperpolarizes the membrane potentials and deactivates these Ca2+ channels in a negative feedback manner, resulting in local, weak Ca2+ responses in spiny dendrites of Purkinje cells.

  4. Actin Dynamics Regulates Voltage-Dependent Calcium-Permeable Channels of the Vicia faba Guard Cell Plasma Membrane

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Liu-Min Fan

    2009-01-01

    Free cytosolic Ca~(2+) ([Ca~(2+)]_(cyt)) is an ubiquitous second messenger in plant cell signaling, and [Ca~(2+)]_(cyt) elevation is associated with Ca~(2+)-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca~(2+) channels and their regulation remains limited in planta. A type of voltage-dependent Ca~(2+)-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba~(2+) and Ca~(2+), and their activities can be inhibited by micromolar Gd~(3+). The unitary conductance and the reversal potential of the channels depend on the Ca~(2+) or Ba~(2+) gradients across the plasma membrane. The inward whole-cell Ca~(2+) (Ba~(2+)) current, as well as the unitary current amplitude and NP. of the single Ca~(2+) channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NP_o of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.

  5. Advanced knowledge of the calcium ion channels on the pulmonary artery smooth muscle cells%肺动脉平滑肌细胞上的钙离子通道研究进展

    Institute of Scientific and Technical Information of China (English)

    姜红妮; 瞿介明

    2011-01-01

    钙离子(Ca2+)为肺动脉平滑肌细胞(PASMC)内至关重要的第二信史,其细胞内浓度的精细变化直接受到多种Ca2+通道的调控.按照细胞内Ca2+的来源,位于细胞膜上,调控细胞外Ca2+进入细胞的通道称为钙内流通道,位于肌质网上调控内质网/肌质网内钙库的Ca2+释放的通道称为钙释放通道.根据Ca2+通道激活方式的不同,Ca2+内流的通道主要分为电压依赖性Ca2+通道(VDCC)和非电压操纵性Ca2+通道(non VDCC).目前发现PASMC上表达的VDCC为CaV 1.2 L型通道,non-VDCC包括受体操纵性通道和钙库操纵性通道.PASMC 上的钙释放通道主要包括三磷酸肌醇受体系统和雷诺定受体系统.这些Ca2+通道通过对细胞内Ca2+的精细调节,使PASMC对各种信号刺激发生反应.%Calcium ion (Ca2+ ) is an extremely crucial second messenger in the pulmonary artery smooth muscle cells (PASMC). The intracellular Ca2+ concentration is finely regulated by multiple Ca2+channels. According to the source of intraeellular Ca2+ , those lie in the cellular membrane and permit the extraeellular Ca2+ to enter into cytoplasm are named as calcium entry channels, and those lie in the sarcoplasmic reticulum and release the Ca2+ stored in it are called calcium release channels. According to pathway of activation, calcium entry channels are divided into voltage-operated Ca2+ channels (VOCC) and non-voltage-dependent Ca2+ channels (non-VOCC). The CaV 1.2 group or L-type VDCC, receptoroperated and store-operated non-VDCC have been found expressed in the PASMC. The calcium release channels mainly include inositol 1,4,5-trisphosphate receptor and Ryanodine receptor. Through the fine adjustment of all these Ca2+ channels, the PASMC react to various stimulus signals.

  6. L-Type Calcium Channels Do Not Play a Critical Role in Chest Blow Induced Ventricular Fibrillation: Commotio Cordis.

    Science.gov (United States)

    Madias, Christopher; Garlitski, Ann C; Kalin, John; Link, Mark S

    2016-01-01

    Background. In a commotio cordis swine model, ventricular fibrillation (VF) can be induced by a ball blow to the chest believed secondary to activation of mechanosensitive ion channels. The purpose of the current study is to evaluate whether stretch induced activation of the L-type calcium channel may cause intracellular calcium overload and underlie the VF in commotio cordis. Method and Results. Anesthetized juvenile swine received 6 chest wall strikes with a 17.9 m/s lacrosse ball timed to the vulnerable period for VF induction. Animals were randomized to IV verapamil (n = 6) or placebo (n = 6). There was no difference in the observed frequency of VF between verapamil (19/26: 73%) and placebo (20/36: 56%) treated animals (p = 0.16). There was also no significant difference in the combined endpoint of VF or nonsustained VF (21/26: 81% in verapamil versus 24/36: 67% in controls, p = 0.22). Conclusions. In this experimental model of commotio cordis, verapamil did not prevent VF induction. Thus, in commotio cordis it is unlikely that stretch activation of the L-type calcium channel with resultant intracellular calcium overload plays a prominent role. PMID:26925288

  7. L-Type Calcium Channels Do Not Play a Critical Role in Chest Blow Induced Ventricular Fibrillation: Commotio Cordis

    Directory of Open Access Journals (Sweden)

    Christopher Madias

    2016-01-01

    Full Text Available Background. In a commotio cordis swine model, ventricular fibrillation (VF can be induced by a ball blow to the chest believed secondary to activation of mechanosensitive ion channels. The purpose of the current study is to evaluate whether stretch induced activation of the L-type calcium channel may cause intracellular calcium overload and underlie the VF in commotio cordis. Method and Results. Anesthetized juvenile swine received 6 chest wall strikes with a 17.9 m/s lacrosse ball timed to the vulnerable period for VF induction. Animals were randomized to IV verapamil (n=6 or placebo (n=6. There was no difference in the observed frequency of VF between verapamil (19/26: 73% and placebo (20/36: 56% treated animals (p=0.16. There was also no significant difference in the combined endpoint of VF or nonsustained VF (21/26: 81% in verapamil versus 24/36: 67% in controls, p=0.22. Conclusions. In this experimental model of commotio cordis, verapamil did not prevent VF induction. Thus, in commotio cordis it is unlikely that stretch activation of the L-type calcium channel with resultant intracellular calcium overload plays a prominent role.

  8. Calcium channel blockade attenuates abnormal synaptic transmission in the dentate gyrus elicited by entorhinal amyloidopathy.

    Science.gov (United States)

    Gholami Pourbadie, Hamid; Naderi, Nima; Janahmadi, Mahyar; Mehranfard, Nasrin; Motamedi, Fereshteh

    2016-10-01

    Entorhinal-hippocampal network is one of the earliest circuits which is affected by Alzheimer's disease (AD). There are numerous data providing the evidence of synaptic deficit in the dentate gyrus (DG) of AD animal model. However, there is little known about how entorhinal cortex (EC) amyloidophaty affects each excitatory and/or inhibitory transmission in the early stage of AD. On the other hand, it is believed that calcium dyshomeostasis has a critical role in the etiology of AD. Here, the effect of the EC amyloid pathogenesis on excitatory or inhibitory post synaptic currents (EPSC and IPSC, respectively) in the DG granule cells and then the possible neuroprotective action of L-type calcium channel blockers (CCBs), nimodipine and isradipine, were examined. The amyloid beta (Aβ) 1-42 was injected bilaterally into the EC of male rats and one week later, synaptic currents in the DG granule cells were assessed by whole cell patch clamp. EPSCs were evoked by stimulating the perforant pathway. Voltage clamp recording showed profound decrease of evoked EPSC amplitude and paired pulse facilitation in the DG granule cells of Aβ treated rats. Furthermore, AMPA/NMDA ratio was significantly decreased in the Aβ treated animals. On the other hand, amplitude of IPSC currents was significantly increased in the DG granule cells of these animals. These modifications of synaptic currents were partially reversed by daily intracerebroventricular administration of isradipine or nimodipine. In conclusion, our results suggest that Aβ in the EC triggers decreased excitatory transmission in the DG with substantial decrement in AMPA currents, leading to a prominent activity of inhibitory circuits and increased inhibition of granule cells which may contribute to the development of AD-related neurological deficits in AD and treatment by CCBs could preserve normal synaptic transmission against Aβ toxicity. PMID:27240164

  9. Fluoride varnishes with calcium glycerophosphate: fluoride release and effect on in vitro enamel demineralization

    Directory of Open Access Journals (Sweden)

    Thiago Saads CARVALHO

    2015-01-01

    Full Text Available The aims of this study were (1 to assess the amount of fluoride (F released from varnishes containing calcium glycerophosphate (CaGP and (2 to assess the effect of the experimental varnishes on in vitro demineralization. Six test groups using 5 varnishes: base varnish (no active ingredients; Duraphat® (2.26% NaF; Duofluorid® (5.63% NaF/CaF2; experimental varnish 1 (1% CaGP/5.63% NaF/CaF2; experimental varnish 2 (5% CaGP/5.63% NaF/CaF2; and no varnish were set up. In stage 1, 60 acrylic blocks were randomly distributed into 6 groups (n = 10. Then 300 µg of each varnish was applied to each block. The blocks were immersed in deionized water, which was changed after 1, 8, 12, 24, 48 and 72 hours. Fluoride concentration in the water was analyzed using a fluoride electrode. In stage 2, 60 bovine enamel samples were distributed into 6 groups (n = 10, and treated with 300 µg of the respective varnish. After 6 h the varnish was removed and the samples were subjected to a 7-day in vitro pH cycle (6 h demineralization/18 h remineralization per day. The demineralization was measured using surface hardness. The results showed that both experimental varnishes released more fluoride than Duofluorid® and Duraphat® (p < 0.05, but Duraphat® showed the best preventive effect by decreasing enamel hardness loss (p < 0.05. Therefore, we conclude that even though (1 the experimental varnishes containing CaGP released greater amounts of F, (2 they did not increase in the preventive effect against enamel demineralization.

  10. Vitamin K3 inhibits mouse uterine contraction in vitro via interference with the calcium transfer and the potassium channels.

    Science.gov (United States)

    Zhang, Xian-Xia; Lu, Li-Min; Wang, Li

    2016-08-01

    Previous studies have demonstrated vitamin K3 had a great relief to smooth muscle spastic disorders, but no researches have yet pinpointed its possible anti-contractile activity in the uterus. Here, we evaluated the effect of vitamin K3 on myometrial contractility and explored the possible mechanisms of vitamin K3 action. Myograph apparatus were used to record the changes in contractility of isolated mouse uterine strips in a tissue bath. Uterine strips were exposed to vitamin K3 or vehicle. Vitamin K3 suppressed spontaneous contractions in a concentration dependent manner. It significantly decreased the contractile frequency induced by PGF2ɑ but not their amplitude (expect 58.0 μM). Prior incubation with vitamin K3 reduced the effectiveness of PGF2ɑ-induced contraction. The antispasmodic effect of vitamin K3 was also sensitive to potassium channel blockers, such as tetraethylammonium, 4-aminopyridine, iberiotoxin) but not to the nitric oxide related pathway blockers. High concentrations (29.0, 58.0 μM) of vitamin K3 weakened the Ca(2+) dose response and inhibited phase 1 contraction (intracellular stored calcium release). These dates suggest that vitamin K3 specifically suppresses myometrial contractility by affecting calcium and potassium channels; thus, this approach has potential therapy for uterine contractile activity related disorders. PMID:27237971

  11. Membrane Properties Involved in Calcium-Stimulated Microparticle Release from the Plasma Membranes of S49 Lymphoma Cells

    Directory of Open Access Journals (Sweden)

    Lauryl E. Campbell

    2014-01-01

    Full Text Available This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32–42°C. A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.

  12. Activation of L-type calcium channels is required for gap junction-mediated intercellular calcium signaling in osteoblastic cells

    DEFF Research Database (Denmark)

    Jørgensen, Niklas Rye; Teilmann, Stefan Cuoni; Henriksen, Zanne;

    2003-01-01

    in "slow" ICW. Human osteoblastic cells transmit intercellular calcium signals by both of these mechanisms. In the current studies we have examined the mechanism of slow gap junction-dependent ICW in osteoblastic cells. In ROS rat osteoblastic cells, gap junction-dependent ICW were inhibited by removal...

  13. Differential release of eicosanoids by bradykinin, arachidonic acid and calcium ionophore A23187 in guinea-pig isolated perfused lung.

    OpenAIRE

    Bakhle, Y. S.; Moncada, S.; de Nucci, G.; Salmon, J A

    1985-01-01

    The effects of infusions of bradykinin (0.2 microM), calcium ionophore A23187 (0.5 microM) and arachidonic acid (13 microM) on the release of eicosanoids from the guinea-pig isolated perfused lung were investigated using radioimmunoassay for thromboxane B2 (TXB2), 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha), PGE2, leukotriene B4 (LTB4) and LTC4 and bioassay using the superfusion cascade. Bradykinin released more 6-oxo-PGF1 alpha than TXB2, whereas arachidonic acid and ionophore released m...

  14. Controlled release of stored optical pulses in an atomic ensemble into two separate photonic channels

    International Nuclear Information System (INIS)

    We report an experiment in which optical pulses stored in an atomic system can be controllably released into two different photonic channels. By controllably turning on the retrieve control pulses at either 795 or 780 nm to read the stored optical pulses in a four-level double Λ-type atomic medium, we can obtain the released probe pulse at 795 or 780 nm, respectively. These readout pulses can be further separated spatially and directed into different optical propagation channels through a grating. Such controlled release of stored optical pulses may extend the capabilities of the quantum information storage technique, and can have applications in multichannel all-optical switching, all-optical routing, quantum information processing, and image storage systems

  15. Self-Setting Calcium Phosphate Cements with Tunable Antibiotic Release Rates for Advanced Antimicrobial Applications.

    Science.gov (United States)

    Ghosh, Shreya; Wu, Victoria; Pernal, Sebastian; Uskoković, Vuk

    2016-03-01

    Osteomyelitis, an infectious disease predominantly tied to poor sanitary conditions in underdeveloped regions of the world, is in need of inexpensive, easily in situ synthesizable and administrable materials for its treatment. The results of this study stem from the attempt to create one such affordable and minimally invasive therapeutic platform in the form of a self-setting, injectable cement with a tunable drug release profile, composed of only nanoparticulate hydroxyapatite, the synthetic version of the bone mineral. Cements comprised two separately synthesized hydroxyapatite powders, one of which, HAP2, was precipitated abruptly, retaining the amorphous nature longer, and the other one of which, HAP1, was precipitated at a slower rate, more rapidly transitioning to the crystalline structure. Cements were made with four different weight ratios of the two hydroxyapatite components: 100/0, 85/15, 50/50, and 0/100 with respect to HAP1 and HAP2. Both the setting and the release rates measured on two different antibiotics, vancomycin and ciprofloxacin, were controlled using the weight ratio of the two hydroxyapatite components. Various inorganic powder properties were formerly used to control drug release, but here we demonstrate for the first time that the kinetics of the mechanism of formation of a solid compound can be controlled to produce tunable drug release profiles. Specifically, it was found that the longer the precursor calcium phosphate component of the cement retains the amorphous nature of the primary precipitate, the more active it was in terms of speeding up the diffusional release of the adsorbed drug. The setting rate was, in contrast, inversely proportional to the release rate and to the content of this active hydroxyapatite component, HAP2. The empirical release profiles were fitted to a set of equations that could be used to tune the release rate to the therapeutic occasion. All of the cements loaded with vancomycin or ciprofloxacin inhibited the

  16. The role of calcium, calcium-activated K+ channels, and tyrosine/kinase in psoralen-evoked responses in human melanoma cells

    Directory of Open Access Journals (Sweden)

    Isoldi M.C.

    2004-01-01

    Full Text Available 8-Methoxy psoralen (8-MOP exerts a short-term (24 h mitogenic action, and a long-term (48-72 h anti-proliferative and melanogenic action on two human melanoma cell lines, SK-Mel 28 and C32TG. An increase of intracellular calcium concentration was observed by spectrofluorometry immediately after the addition of 0.1 mM 8-MOP to both cell lines, previously incubated with calcium probe fluo-3 AM (5 µM. The intracellular Ca2+ chelator BAPTA/AM (1 µM blocked both early (mitogenic and late (anti-proliferative and melanogenic 8-MOP effects on both cell lines, thus revealing the importance of the calcium signal in both short- and long-term 8-MOP-evoked responses. Long-term biological assays with 5 and 10 mM tetraethylammonium chloride (TEA, an inhibitor of Ca2+-dependent K+ channels did not affect the responses to psoralen; however, in 24-h assays 10 mM TEA blocked the proliferative peak, indicating a modulation of Ca2+-dependent K+ channels by 8-MOP. No alteration of cAMP basal levels or forskolin-stimulated cAMP levels was promoted by 8-MOP in SK-Mel 28 cells, as determined by radioimmunoassay. However, in C32TG cells forskolin-stimulated cAMP levels were further increased in the presence of 8-MOP. In addition, assays with 1 µM protein kinase C and calcium/calmodulin-dependent kinase inhibitors, Ro 31-8220 and KN-93, respectively, excluded the participation of these kinases in the responses evoked by 8-MOP. Western blot with antibodies anti-phosphotyrosine indicated a 92% increase of the phosphorylated state of a 43-kDa band, suggesting that the phosphorylation of this protein is a component of the cascade that leads to the increase of tyrosinase activity.

  17. The role of voltage-gated calcium channels in neurotransmitter phenotype specification: Coexpression and functional analysis in Xenopus laevis.

    Science.gov (United States)

    Lewis, Brittany B; Miller, Lauren E; Herbst, Wendy A; Saha, Margaret S

    2014-08-01

    Calcium activity has been implicated in many neurodevelopmental events, including the specification of neurotransmitter phenotypes. Higher levels of calcium activity lead to an increased number of inhibitory neural phenotypes, whereas lower levels of calcium activity lead to excitatory neural phenotypes. Voltage-gated calcium channels (VGCCs) allow for rapid calcium entry and are expressed during early neural stages, making them likely regulators of activity-dependent neurotransmitter phenotype specification. To test this hypothesis, multiplex fluorescent in situ hybridization was used to characterize the coexpression of eight VGCC α1 subunits with the excitatory and inhibitory neural markers xVGlut1 and xVIAAT in Xenopus laevis embryos. VGCC coexpression was higher with xVGlut1 than xVIAAT, especially in the hindbrain, spinal cord, and cranial nerves. Calcium activity was also analyzed on a single-cell level, and spike frequency was correlated with the expression of VGCC α1 subunits in cell culture. Cells expressing Cav 2.1 and Cav 2.2 displayed increased calcium spiking compared with cells not expressing this marker. The VGCC antagonist diltiazem and agonist (-)BayK 8644 were used to manipulate calcium activity. Diltiazem exposure increased the number of glutamatergic cells and decreased the number of γ-aminobutyric acid (GABA)ergic cells, whereas (-)BayK 8644 exposure decreased the number of glutamatergic cells without having an effect on the number of GABAergic cells. Given that the expression and functional manipulation of VGCCs are correlated with neurotransmitter phenotype in some, but not all, experiments, VGCCs likely act in combination with a variety of other signaling factors to determine neuronal phenotype specification. PMID:24477801

  18. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

    Science.gov (United States)

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H

    2014-11-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

  19. Molecular basis of toxicity of N-type calcium channel inhibitor MVIIA.

    Science.gov (United States)

    Wang, Fei; Yan, Zhenzhen; Liu, Zhuguo; Wang, Sheng; Wu, Qiaoling; Yu, Shuo; Ding, Jiuping; Dai, Qiuyun

    2016-02-01

    MVIIA (ziconotide) is a specific inhibitor of N-type calcium channel, Cav2.2. It is derived from Cone snail and currently used for the treatment of severe chronic pains in patients unresponsive to opioid therapy. However, MVIIA produces severe side-effects, including dizziness, nystagmus, somnolence, abnormal gait, and ataxia, that limit its wider application. We previously identified a novel inhibitor of Cav2.2, ω-conopeptide SO-3, which possesses similar structure and analgesic activity to MVIIA's. To investigate the key residues for MVIIA toxicity, MVIIA/SO-3 hybrids and MVIIA variants carrying mutations in its loop 2 were synthesized. The substitution of MVIIA's loop 1 with the loop 1 of SO-3 resulted in significantly reduced Cav2.2 binding activity in vitro; the replacement of MVIIA loop 2 by the loop 2 of SO-3 not only enhanced the peptide/Cav2.2 binding but also decreased its toxicity on goldfish, attenuated mouse tremor symptom, spontaneous locomotor activity, and coordinated locomotion function. Further mutation analysis and molecular calculation revealed that the toxicity of MVIIA mainly arose from Met(12) in the loop 2, and this residue inserts into a hydrophobic hole (Ile(300), Phe(302) and Leu(305)) located between repeats II and III of Cav2.2. The combinative mutations of the loop 2 of MVIIA or other ω-conopeptides may be used for future development of more effective Cav2.2 inhibitors with lower side effects. PMID:26344359

  20. Effect of endothelin-1 on calcium channel gating by agonists in vascular smooth muscle

    International Nuclear Information System (INIS)

    Rat isolated aorta was more sensitive to the contractile effect of endothelin-1 (ET-1) when the endothelium was removed. ET-1 was more potent on mesenteric resistance arteries than on aorta. A threshold concentration of ET-1 (100 pM) enhanced the contractile responses of aortic rings to Bay K 8644 and clonidine, especially in the absence of endothelium. Potentiation of clonidine-evoked contraction was accompanied by an enhancement of 45Ca influx and was abolished by nifedipine. These actions of ET-1 (100 pM) could not be attributed to a decrease in membrane potential or in cAMP levels. ET-1 (100 pM) decreased cGMP in intact aortic rings, which could contribute to its actions in the presence of endothelium. Removal of endothelium reduced cGMP levels and these were not further decreased by ET-1. Since ET-1 exerted a pronounced potentiating effect in the absence of endothelium, it is likely that ET-1 modulates calcium channels by an additional mechanism, unrelated to cyclic nucleotides

  1. Radioprotective effect of calcium channel blocker, diltiazem on survival in gamma rays exposed mice

    International Nuclear Information System (INIS)

    Diltiazem, a calcium channel blocker, used widely in cardio-vascular therapy, protected mice against death and weight loss due to ionising radiation. Administration of such compound 30 minutes prior to 8.0 Gy gamma irradiation enhanced the 30 days survival of animals to 37.5 and 82.5 percent at the dose of 50 and 100 mg/kg b. wt., respectively. On the contrary, 100 per cent death was noted at the dose of 25 mg and 82.5 percent at 200 mg/kg b.wt. Pre-treatment with a dose of 100 mg/kg b.wt. enhanced 30 day survival after lethal irradiation and also inhibited the radiation induced life span shortening. Prior treatment of diltiazem accelerated the recovery of radiation induced weight loss also. Data on dose response demonstrate that higher dose of diltiazem (up to 100 mg/kg b.wt.) is more effective against lethal gamma radiation dose. However, doses above 100 mg/kg b. wt. was found to be quite ineffective in preventing mice against deleterious effects of radiation. (author)

  2. T-type Calcium Channel Regulation of Neural Tube Closure and EphrinA/EPHA Expression

    Directory of Open Access Journals (Sweden)

    Sarah Abdul-Wajid

    2015-10-01

    Full Text Available A major class of human birth defects arise from aberrations during neural tube closure (NTC. We report on a NTC signaling pathway requiring T-type calcium channels (TTCCs that is conserved between primitive chordates (Ciona and Xenopus. With loss of TTCCs, there is a failure to seal the anterior neural folds. Accompanying loss of TTCCs is an upregulation of EphrinA effectors. Ephrin signaling is known to be important in NTC, and ephrins can affect both cell adhesion and repulsion. In Ciona, ephrinA-d expression is downregulated at the end of neurulation, whereas, with loss of TTCC, ephrinA-d remains elevated. Accordingly, overexpression of ephrinA-d phenocopied TTCC loss of function, while overexpression of a dominant-negative Ephrin receptor was able to rescue NTC in a Ciona TTCC mutant. We hypothesize that signaling through TTCCs is necessary for proper anterior NTC through downregulation of ephrins, and possibly elimination of a repulsive signal.

  3. Polyaniline-graphene oxide nanocomposite sensor for quantification of calcium channel blocker levamlodipine.

    Science.gov (United States)

    Jain, Rajeev; Sinha, Ankita; Khan, Ab Lateef

    2016-08-01

    A novel polyaniline-graphene oxide nanocomposite (PANI/GO/GCE) sensor has been fabricated for quantification of a calcium channel blocker drug levamlodipine (LAMP). Fabricated sensor has been characterized by electrochemical impedance spectroscopy, square wave and cyclic voltammetry, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The developed PANI/GO/GCE sensor has excellent analytical performance towards electrocatalytic oxidation as compared to PANI/GCE, GO/GCE and bare GCE. Under optimized experimental conditions, the fabricated sensor exhibits a linear response for LAMP for its oxidation over a concentration range from 1.25μgmL(-1) to 13.25μgmL(-1) with correlation coefficient of 0.9950 (r(2)), detection limit of 1.07ngmL(-1) and quantification limit of 3.57ngmL(-1). The sensor shows an excellent performance for detecting LAMP with reproducibility of 2.78% relative standard deviation (RSD). The proposed method has been successfully applied for LAMP determination in pharmaceutical formulation with a recovery from 99.88% to 101.75%. PMID:27157745

  4. The Low-Threshold Calcium Channel Cav3.2 Determines Low-Threshold Mechanoreceptor Function

    Directory of Open Access Journals (Sweden)

    Amaury François

    2015-01-01

    Full Text Available The T-type calcium channel Cav3.2 emerges as a key regulator of sensory functions, but its expression pattern within primary afferent neurons and its contribution to modality-specific signaling remain obscure. Here, we elucidate this issue using a unique knockin/flox mouse strain wherein Cav3.2 is replaced by a functional Cav3.2-surface-ecliptic GFP fusion. We demonstrate that Cav3.2 is a selective marker of two major low-threshold mechanoreceptors (LTMRs, Aδ- and C-LTMRs, innervating the most abundant skin hair follicles. The presence of Cav3.2 along LTMR-fiber trajectories is consistent with critical roles at multiple sites, setting their strong excitability. Strikingly, the C-LTMR-specific knockout uncovers that Cav3.2 regulates light-touch perception and noxious mechanical cold and chemical sensations and is essential to build up that debilitates allodynic symptoms of neuropathic pain, a mechanism thought to be entirely A-LTMR specific. Collectively, our findings support a fundamental role for Cav3.2 in touch/pain pathophysiology, validating their critic pharmacological relevance to relieve mechanical and cold allodynia.

  5. eNOS-dependent antisenscence effect of a calcium channel blocker in human endothelial cells.

    Directory of Open Access Journals (Sweden)

    Toshio Hayashi

    Full Text Available Senescence of vascular endothelial cells is an important contributor to the pathogenesis of age-associated vascular disorders such as atherosclerosis. We investigated the effects of antihypertensive agents on high glucose-induced cellular senescence in human umbilical venous endothelial cells (HUVECs. Exposure of HUVECs to high glucose (22 mM for 3 days increased senescence-associated- β-galactosidase (SA-β-gal activity, a senescence marker, and decreased telomerase activity, a replicative senescence marker. The calcium channel blocker nifedipine, but not the β1-adrenergic blocking agent atenolol or the angiotensin-converting enzyme inhibitor perindopril, reduced SA-β-gal positive cells and prevented a decrease in telomerase activity in a high-glucose environment. This beneficial effect of nifedipine was associated with reduced reactive oxygen species (ROS and increased endothelial nitric oxide synthase (eNOS activity. Thus, nifedipine prevented high glucose-induced ROS generation and increased basal eNOS phosphorylation level at Ser-1177. Treatment with N (G-nitro-L-arginine (L-NAME and transfection of small interfering RNA (siRNA targeting eNOS eliminated the anti-senscence effect of nifedipine. These results demonstrate that nifedipine can prevent endothelial cell senescence in an eNOS-dependent manner. The anti-senescence action of nifedipine may represent a novel mechanism by which it protects against atherosclerosis.

  6. Degradation kinetics and pathways of three calcium channel blockers under UV irradiation.

    Science.gov (United States)

    Zhu, Bing; Zonja, Bozo; Gonzalez, Oscar; Sans, Carme; Pérez, Sandra; Barceló, Damia; Esplugas, Santiago; Xu, Ke; Qiang, Zhimin

    2015-12-01

    Calcium channel blockers (CCBs) are a group of pharmaceuticals widely prescribed to lower blood pressure and treat heart diseases. They have been frequently detected in wastewater treatment plant (WWTP) effluents and downstream river waters, thus inducing a potential risk to aquatic ecosystems. However, little is known about the behavior and fate of CCBs under UV irradiation, which has been adopted as a primary disinfection method for WWTP effluents. This study investigated the degradation kinetics and pathways of three commonly-used CCBs, including amlodipine (AML), diltiazem (DIL), and verapamil (VER), under UV (254 nm) irradiation. The chemical structures of transformation byproducts (TBPs) were first identified to assess the potential ecological hazards. On that basis, a generic solid-phase extraction method, which simultaneously used four different cartridges, was adopted to extract and enrich the TBPs. Thereafter, the photo-degradation of target CCBs was performed under UV fluences typical for WWTP effluent disinfection. The degradation of all three CCBs conformed to the pseudo-first-order kinetics, with rate constants of 0.031, 0.044 and 0.011 min(-1) for AML, DIL and VER, respectively. By comparing the MS(2) fragments and the evolution (i.e., formation or decay) trends of identified TBPs, the degradation pathways were proposed. In the WWTP effluent, although the target CCBs could be degraded, several TBPs still contained the functional pharmacophores and reached peak concentrations under UV fluences of 40-100 mJ cm(-2).

  7. Cilnidipine, but not amlodipine, ameliorates osteoporosis in ovariectomized hypertensive rats through inhibition of the N-type calcium channel.

    Science.gov (United States)

    Shimizu, Hideo; Nakagami, Hironori; Yasumasa, Natsuki; Mariana, Osako Kiomy; Kyutoku, Mariko; Koriyama, Hiroshi; Nakagami, Futoshi; Shimamura, Munehisa; Rakugi, Hiromi; Morishita, Ryuichi

    2012-01-01

    Both osteoporosis and high blood pressure are major diseases in aging populations. Recent studies demonstrated that some antihypertensive drugs reduced the risk of bone fracture in elderly patients. Although calcium channel blockers (CCB) are widely used as first-line antihypertensive agents, there is no evidence that they prevent osteoporosis. In this study, we investigated the effects of two types of CCB on bone metabolism: cilnidipine (L-/N-type CCB), which suppresses norepinephrine release from the sympathetic nerve, and amlodipine (L-type CCB). In ovariectomized female spontaneous hypertensive rats, administration of cilnidipine, but not amlodipine, resulted in a significant increase in the ratio of alkaline phosphatase to tartrate-resistant acid phosphatase (TRAP) and a decrease in the number of osteoclasts, as assessed by TRAP staining in the proximal tibia. Bone mineral density, moreover, was significantly higher in the cilnidipine group as compared with the amlodipine group and was associated with a significant decrease in a urinary collagen degradation product (deoxypyridinoline). The degree of prevention of osteoporosis by cilnidipine was similar to that of carvedilol (a β-blocker) because β-blockers reduce fracture risks though the inhibition of osteoclast activation. Interestingly, these effects cannot be attributed to the reduction of blood pressure because all three drugs significantly decreased blood pressure. In contrast, both cilnidipine and carvedilol, but not amlodipine, significantly decreased heart rate, indicating that both cilnidipine and carvedilol suppressed sympathetic nervous activity. Overall, our present data showed that cilnidipine (L-/N-type CCB) ameliorated osteoporosis in ovariectomized hypertensive rats. These pleiotropic effects of antihypertensive drugs such as cilnidipine and carvedilol might provide additional benefits in the treatment of hypertensive postmenopausal women.

  8. Comprehensive behavioral analysis of voltage-gated calcium channel beta-anchoring and -regulatory protein knockout mice

    Directory of Open Access Journals (Sweden)

    Akito eNakao

    2015-06-01

    Full Text Available Calcium (Ca2+ influx through voltage-gated Ca2+ channels (VGCCs induces numerous intracellular events such as neuronal excitability, neurotransmitter release, synaptic plasticity, and gene regulation. It has been shown that genes related to Ca2+ signaling, such as the CACNA1C, CACNB2, and CACNA1I genes that encode VGCC subunits, are associated with schizophrenia and other psychiatric disorders. Recently, VGCC beta-anchoring and -regulatory protein (BARP was identified as a novel regulator of VGCC activity via the interaction of VGCC β subunits. To examine the role of the BARP in higher brain functions, we generated BARP knockout (KO mice and conducted a comprehensive battery of behavioral tests. BARP KO mice exhibited greatly reduced locomotor activity, as evidenced by decreased vertical activity, stereotypic counts in the open field test, and activity level in the home cage, and longer latency to complete a session in spontaneous T-maze alteration test, which reached study-wide significance. Acoustic startle response was also reduced in the mutants. Interestingly, they showed multiple behavioral phenotypes that are seemingly opposite to those seen in the mouse models of schizophrenia and its related disorders, including increased working memory, flexibility, prepulse inhibition, and social interaction, and decreased locomotor activity, though many of these phenotypes are statistically weak and require further replications. These results demonstrate that BARP is involved in the regulation of locomotor activity and, possibly, emotionality. The possibility was also suggested that BARP KO mice may serve as a unique tool for investigating the pathogenesis/pathophysiology of schizophrenia and related disorders. Further evaluation of the molecular and physiological phenotypes of the mutant mice would provide new insights into the role of BARP in higher brain functions.

  9. Atypical properties of a conventional calcium channel β subunit from the platyhelminth Schistosoma mansoni

    Directory of Open Access Journals (Sweden)

    Schneider Toni

    2008-03-01

    Full Text Available Abstract Background The function of voltage-gated calcium (Cav channels greatly depends on coupling to cytoplasmic accessory β subunits, which not only promote surface expression, but also modulate gating and kinetic properties of the α1 subunit. Schistosomes, parasitic platyhelminths that cause schistosomiasis, express two β subunit subtypes: a structurally conventional β subunit and a variant β subunit with unusual functional properties. We have previously characterized the functional properties of the variant Cavβ subunit. Here, we focus on the modulatory phenotype of the conventional Cavβ subunit (SmCavβ using the human Cav2.3 channel as the substrate for SmCavβ and the whole-cell patch-clamp technique. Results The conventional Schistosoma mansoni Cavβ subunit markedly increases Cav2.3 currents, slows macroscopic inactivation and shifts steady state inactivation in the hyperpolarizing direction. However, currents produced by Cav2.3 in the presence of SmCavβ run-down to approximately 75% of their initial amplitudes within two minutes of establishing the whole-cell configuration. This suppressive effect was independent of Ca2+, but dependent on intracellular Mg2+-ATP. Additional experiments revealed that SmCavβ lends the Cav2.3/SmCavβ complex sensitivity to Na+ ions. A mutant version of the Cavβ subunit lacking the first forty-six amino acids, including a string of twenty-two acidic residues, no longer conferred sensitivity to intracellular Mg2+-ATP and Na+ ions, while continuing to show wild type modulation of current amplitude and inactivation of Cav2.3. Conclusion The data presented in this article provide insights into novel mechanisms employed by platyhelminth Cavβ subunits to modulate voltage-gated Ca2+ currents that indicate interactions between the Ca2+ channel complex and chelated forms of ATP as well as Na+ ions. These results have potentially important implications for understanding previously unknown mechanisms by

  10. First direct electron microscopic visualization of a tight spatial coupling between GABAA-receptors and voltage-sensitive calcium channels

    DEFF Research Database (Denmark)

    Hansen, Gert Helge; Belhage, B; Schousboe, A

    1992-01-01

    Using cerebellar granule neurons in culture it was demonstrated that exposure of the cells to the GABAA receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) leads to an increase in the number of voltage-gated calcium channels as revealed by quantitative preembedding indirect...... immunogold labelling using a monoclonal antibody specific for phenylalkylamine and dihydropyridine sensitive Ca2+ channels. Using the same technique and a monoclonal antibody (bd-17) to the beta 2/beta 3-subunit of the GABAA-receptor, double labelling of Ca2+ channels and GABAA-receptors with gold particles...... of different and well defined sizes were performed. This showed that in THIP-treated cultures 20% of GABAA-receptors in cell processes were located in close proximity (i.e. within 40 nm) of Ca2+ channels in the plasma membrane. This was not observed in non-treated cultures nor was it observed in cell...

  11. Calcium-dependent expression of transient receptor potential canonical type 3 channels in patients with chronic kidney disease

    DEFF Research Database (Denmark)

    Liu, Ying; Krueger, Katharina; Hovsepian, Anahit;

    2011-01-01

    It is unknown whether extracellular calcium may regulate the expression of transient receptor potential canonical type 3 (TRPC3) channels in patients with chronic kidney disease. Using quantitative in-cell Western assay we compared the expression of TRPC3 channel protein in monocytes from 20...... patients with chronic kidney disease and 19 age- and sex-matched healthy control subjects. TRPC3 channels were identified by immunoblotting using specific antibodies and TRPC3 protein was further confirmed by mass spectrometry. We observed a significant increase of TRPC3 channel protein expression...... in patients with chronic kidney disease compared to healthy control subjects (normalized expression, 0.42±0.06 vs. 0.19±0.03; p...

  12. "Synthesis and smooth muscle Calcium channel antagonist effects of new derivatives of 1,4-Dihydropyridine containing Nitroimidazol substituent "

    Directory of Open Access Journals (Sweden)

    Miri R

    2002-09-01

    Full Text Available A group of racemic 3-[(2-hydroxyethyl, (2-Methoxyethyl, (2-acetylethyl or (2-cyanoethyl], 5- methyl, ethyl or isopropyl-1, 4-dihydro-2, 6-dimethyl-4-(1-methyl-5-nitro-2-imidazolyl-3, 5-pyridinedicarboxylates [XIV-XXV] were prepared by the reaction of 1-methyl-5-nitroimidazol-2-carboxaldehyde [X] with acetoacetic esters [VI-IX] and alkys 3-aminocrotonate [XI-XIII]. In vitro calcium channel antagonist activities of the tested compounds were determined by their effects on contraction of Guinea Pig Ileal Longitudinal Smooth Muscle (GPILSM which was induced by carbacol (1.67 χ 10^-7 M. All compounds exhibited calcium channel antagonist activity (IC50=10^-12 to 10^-13 M range comparable to nifedipine as reference drug (IC50=1.07±0.12x 10^-11 M.

  13. Interaction of SR 33557 with skeletal muscle calcium channel blocker receptors in the baboon: characterization of its binding sites

    International Nuclear Information System (INIS)

    A procedure for the isolation of primate skeletal microsomal membranes was initiated. Membranes exhibited specific enzymatic markers such as 5'-nucleotidase, Ca2+,Mg(2+)-adenosine triphosphatase and an ATP-dependent calcium uptake. Baboon skeletal microsomes bound specifically with high-affinity potent Ca2+ channel blockers such as dihydropyridine, phenylalkylamine and benzothiazepine derivatives. Scatchard analysis of equilibrium binding assays with [3H](+)-PN 200-110, [3H](-)-desmethoxyverapamil [( 3H](-)-D888) and [3H]-d-cis-dilitiazem were consistent with a single class of binding sites for the three radioligands. The pharmacological profile of SR 33557, an original compound with calcium antagonist properties, was investigated using radioligand binding studies. SR 33557 totally inhibited the specific binding of the three main classes of Ca2+ channel effectors and interacted allosterically with them. In addition, SR 33557 bound with high affinity to a homogeneous population of binding sites in baboon skeletal muscle

  14. Soil Manganese and Iron Released due to Calcium Salts:Bioavailability to Pepper (Capsicum frutescens L.)

    Institute of Scientific and Technical Information of China (English)

    SI You-Bin; ZHOU Jing; ZHOU Dong-Mei; CHEN Huai-Man

    2004-01-01

    Releases of manganese and iron ions from an albic soil (Albic-Udic Luvisol), a yellow-red soil (Hap-Udic Ferrisol) and a yellow-brown soil (Arp-Udic Luvisol) induced by calcium salt addition and their bioavailability to pepper (Capsicum frutescens L.) were studied in a pot experiment. Addition of Ca(NO3)2 decreased soil pH and increased both exchangeable and DTPA (diethylenetriamine pentaacetic acid)-extractable Mn and Fe in soils. Meanwhile, total Mn accumulation in the shoots of Capsicum frutescens L. on the salt-treated soils increased significantly (P < 0.01) compared with the control, suggesting that salt addition to soil induced Mn toxicity in Capsicum frutescens L. Although exchangeable and DTPA-extractable Fe increased also in the salt-treated soils, Fe uptake by the shoots of Capsicum frutescens L. decreased. The effect of added salts in soils on dry matter weight of pepper varied with the soil characteristics, showing different buffer capacities of the soils for salt toxicity in an order of yellow-brown soil > albic soil > yellow-red soil. Fe/Mn ratio in shoots of Capsicum frutescens L. decreased with increasing salt addition for all the soils, which was ascribed to the antagonistic effect of Mn on Fe accumulation. The ratio of Fe/Mn in the tissue was a better indicator of the appearance of Mn toxicity symptoms than Mn concentration alone.

  15. Interleukin-2 stimulates osteoclastic activity: Increased acid production and radioactive calcium release

    International Nuclear Information System (INIS)

    Recombinant human interleukin-2 (IL-2) was studied to determine effects on acid production by individual osteoclasts in situ on mouse calvarial bones. This analysis was performed using a microspectrofluorimetric technique to quantify acid production in individual cells. Radioactive calcium release was determined using calvarial bones in a standard tissue culture system. This allowed us to correlate changes in acid production with a measure of bone resorption. IL-2 stimulated acid production and bone resorbing activity. Both effects were inhibited by calcitonin. No stimulation of bone resorption occurred when IL-2-containing test media was incubated with a specific anti-IL-2 antibody and ultrafiltered. Our data demonstrated a correlation between acid production and bone resorbing activity in mouse calvaria exposed to parathyroid hormone (PTH). The data obtained from cultured mouse calvaria exposed to IL-2 demonstrated similar stimulatory effects to those seen during PTH exposure. These data suggest that calvaria exposed to IL-2 in vitro have increased osteoclastic acid production corresponding with increased bone resorption. (author)

  16. Somatic and germline CACNA1D calcium channel mutations in aldosterone-producing adenomas and primary aldosteronism

    OpenAIRE

    Scholl, Ute I; Goh, Gerald; Stölting, Gabriel; de Oliveira, Regina Campos; Choi, Murim; Overton, John D; Fonseca, Annabelle L.; Korah, Reju; Lee F. Starker; Kunstman, John W.; Prasad, Manju L.; Hartung, Erum A.; Mauras, Nelly; Benson, Matthew R.; Brady, Tammy

    2013-01-01

    Adrenal aldosterone-producing adenomas (APAs) constitutively produce the salt-retaining hormone aldosterone and are a common cause of severe hypertension. Recurrent mutations in the potassium channel KCNJ5 that result in cell depolarization and Ca2+ influx cause ~40% of these tumors 1 . We found five somatic mutations (four altering glycine 403, one altering isoleucine 770) in CACNA1D, encoding a voltage-gated calcium channel, among 43 non-KCNJ5-mutant APAs. These mutations lie in S6 segments...

  17. Neuroprotective effect of gadolinium: a stretch-activated calcium channel blocker in mouse model of ischemia-reperfusion injury.

    Science.gov (United States)

    Gulati, Puja; Muthuraman, Arunachalam; Jaggi, Amteshwar S; Singh, Nirmal

    2013-03-01

    The present study was designed to investigate the potential of gadolinium, a stretch-activated calcium channel blocker in ischemic reperfusion (I/R)-induced brain injury in mice. Bilateral carotid artery occlusion of 12 min followed by reperfusion for 24 h was given to induce cerebral injury in male Swiss mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using Morris water maze test and motor incoordination was evaluated using rota-rod, lateral push, and inclined beam walking tests. In addition, total calcium, thiobarbituric acid reactive substance (TBARS), reduced glutathione (GSH), and acetylcholinesterase (AChE) activity were also estimated in brain tissue. I/R injury produced a significant increase in cerebral infarct size. A significant loss of memory along with impairment of motor performance was also noted. Furthermore, I/R injury also produced a significant increase in levels of TBARS, total calcium, AChE activity, and a decrease in GSH levels. Pretreatment of gadolinium significantly attenuated I/R-induced infarct size, behavioral and biochemical changes. On the basis of the present findings, we can suggest that opening of stretch-activated calcium channel may play a critical role in ischemic reperfusion-induced brain injury and that gadolinium has neuroprotective potential in I/R-induced injury.

  18. Targeting voltage-gated calcium channels: developments in peptide and small-molecule inhibitors for the treatment of neuropathic pain

    OpenAIRE

    Vink, S.; Alewood, PF

    2012-01-01

    Chronic pain affects approximately 20% of people worldwide and places a large economic and social burden on society. Despite the availability of a range of analgesics, this condition is inadequately treated, with complete alleviation of symptoms rarely occurring. In the past 30 years, the voltage-gated calcium channels (VGCCs) have been recognized as potential targets for analgesic development. Although the majority of the research has been focused on Cav2.2 in particular, other VGCC subtypes...

  19. Absence of the ER Cation Channel TMEM38B/TRIC-B Disrupts Intracellular Calcium Homeostasis and Dysregulates Collagen Synthesis in Recessive Osteogenesis Imperfecta.

    Directory of Open Access Journals (Sweden)

    Wayne A Cabral

    2016-07-01

    Full Text Available Recessive osteogenesis imperfecta (OI is caused by defects in proteins involved in post-translational interactions with type I collagen. Recently, a novel form of moderately severe OI caused by null mutations in TMEM38B was identified. TMEM38B encodes the ER membrane monovalent cation channel, TRIC-B, proposed to counterbalance IP3R-mediated Ca2+ release from intracellular stores. The molecular mechanisms by which TMEM38B mutations cause OI are unknown. We identified 3 probands with recessive defects in TMEM38B. TRIC-B protein is undetectable in proband fibroblasts and osteoblasts, although reduced TMEM38B transcripts are present. TRIC-B deficiency causes impaired release of ER luminal Ca2+, associated with deficient store-operated calcium entry, although SERCA and IP3R have normal stability. Notably, steady state ER Ca2+ is unchanged in TRIC-B deficiency, supporting a role for TRIC-B in the kinetics of ER calcium depletion and recovery. The disturbed Ca2+ flux causes ER stress and increased BiP, and dysregulates synthesis of proband type I collagen at multiple steps. Collagen helical lysine hydroxylation is reduced, while telopeptide hydroxylation is increased, despite increased LH1 and decreased Ca2+-dependent FKBP65, respectively. Although PDI levels are maintained, procollagen chain assembly is delayed in proband cells. The resulting misfolded collagen is substantially retained in TRIC-B null cells, consistent with a 50-70% reduction in secreted collagen. Lower-stability forms of collagen that elude proteasomal degradation are not incorporated into extracellular matrix, which contains only normal stability collagen, resulting in matrix insufficiency. These data support a role for TRIC-B in intracellular Ca2+ homeostasis, and demonstrate that absence of TMEM38B causes OI by dysregulation of calcium flux kinetics in the ER, impacting multiple collagen-specific chaperones and modifying enzymes.

  20. Synthesis and Effects of Novel Dihydropyridines as Dual Calcium Channel Blocker and Angiotensin Antagonist on Isolated Rat Aorta

    Directory of Open Access Journals (Sweden)

    Farzin Hadizadeh

    2010-01-01

    Full Text Available Four novel losartan analogues 5a-d were synthesized by connecting a dihydropyridine nucleus to imidazole ring. The effects of 5a and 5b on angiotensin receptors (AT1 and L-type calcium channels were investigated on isolated rat aorta. Materials and MethodsAortic rings were pre-contracted with 1 µM Angiotensin II or 80 mM KCl and relaxant effects of losartan, nifedipine, 5a and 5b were evaluated by cumulative addition of these drugs to the bath solution.ResultsThe results showed that compounds 5a and 5b have both L-type calcium channel and AT1 receptor blocking activity. Their effects on AT1 receptors are 1000 and 100,000 times more than losartan respectively. The activity of compound 5b on L-type calcium channel is significantly less than nifedipine but compound 5a has comparable effect with nifedipine. ConclusionFinally we concluded that these two new Compounds can be potential candidates to be used as effective antihypertensive agents.

  1. CNS Voltage-gated Calcium Channel Gene Variation And Prolonged Recovery Following Sport-related Concussion

    Science.gov (United States)

    McDevitt, Jane

    2016-01-01

    Objectives: To examine the association between concussion duration and two calcium channel, voltage-dependent, R type, alpha 1E subunit (CACNA1E) single nucleotide polymorphisms (i.e., rs35737760 and rs704326). A secondary purpose was to examine the association between CACNA1E single nucleotide polymorphisms (SNPs) and three acute concussion severity scores (i.e., vestibule-ocular reflex test, balance error scoring scale, and Immediate Post-Concussion Assessment and Cognitive Testing). Methods: Forty athletes with a diagnosed concussion from a hospital concussion program completed a standardized initial evaluation. Concussion injury characteristics, acute signs and symptoms followed by an objective screening (i.e., vestibular ocular assessments, balance error scoring system test, and Immediate Post-Concussion Assessment and Cognitive Testing exam) were assessed. Enrolled participants provided salivary samples for isolation of DNA. Two exon SNPs rs35737760 and rs704326 within CACNA1E were genotyped. Results: There was a significant difference found between acute balance deficits and prolonged recovery group (X2 = 5.66, p = 0.017). There was an association found between the dominant model GG genotype (X2 = 5.41, p = 0.027) within the rs704326 SNP and prolonged recovery group. Significant differences were identified for the rs704326 SNP within the dominant model GG genotype (p = 0.030) for VOR scores by recovery. A significant difference was found between the rs704326 SNP codominant model AA (p = 0.042) and visual memory. There was an association between acute balance deficits and prolonged recovery (X2 = 5.66, p = 0.017) for the rs35737760 SNP. No significant associations between concussion severity and genotype for rs35737760 SNP. Conclusion: Athletes carrying the CACNA1E rs704326 homozygous genotype GG are at a greater risk of a prolonged recovery. Athletes that reported balance deficits at the time of injury were more likely to have prolonged recovery. These

  2. Stimulation of beta-adrenoceptors inhibits calcium-dependent potassium-channels in mouse macrophages

    Energy Technology Data Exchange (ETDEWEB)

    Rosati, C.; Hannaert, P.; Dausse, J.P.; Braquet, P.; Garay, R.

    1986-12-01

    K/sup +/ efflux in mouse macrophages exhibited a rate constant (k/sub k/) of 0.67 +/- 0.04 (h)/sup -1/. This was strongly stimulated by increasing concentrations of the Ca/sup 2 +/ ionophore A23187 up to a maximal value of 4.01 +/- 0.25 (h)/sup -1/ with an IC/sub 50/ of 7.6 +/- 1.9 ..mu..M. Similar results were obtained with the Ca/sup 2 +/ ionophore ionomycin. Binding experiments with /sup 3/H-dihydroalprenolol revealed a high density of beta-adrenergic receptors with apparent dissociation constant of 2.03 +/- 0.06 nM. Isoproterenol at a concentration of 10/sup -6/ -10/sup -5/ M induced a two- to threefold stimulation of endogenous levels of cyclic AMP (cAMP). A23187-stimulated K/sup +/ efflux was partially inhibited by (i) stimulation of adenylate cyclase with isoproterenol, forskolin or, PGE/sub 1/; (ii) exogenous cAMP; and (iii) inhibition of phosphodiesterase with MIX (1-methyl-3-isobutylxanthine). Maximal inhibition of K/sup +/ efflux was obtained by simultaneous addition of isoproterenol and MIX. In dose-response curves, the isoproterenol-sensitive K/sup +/ efflux was half-maximally inhibited (IC/sub 50/) with 2-5 x 10/sup -10/ M of isoproterenol concentration. Propranolol was able to completely block the effect of isoproterenol, with an IC/sub 50/ of about 1-2 x 10/sup -7/ M. Isoproterenol and MIX did not inhibit A23187-stimulated K/sup +/ efflux in an incubation medium where NaCl was replaced by sucrose (or choline), suggesting the involvement of an Na/sup +/:Ca/sup 2 +/ exchange mechanism. The results show that stimulation of beta-adrenoceptors in mouse macrophages counter balances the opening of K/sup +/ channels induced by the calcium ionophore A23187. This likely reflects a decrease in cytoslic free calcium content via a cAMP-mediated stimulation of Na/sup +/:Ca/sup 2 +/ exchange.

  3. Intracellular calcium stores drive slow non-ribbon vesicle release from rod photoreceptors

    OpenAIRE

    Minghui eChen; David eKrizaj; Thoreson, Wallace B

    2014-01-01

    Rods are capable of greater slow release than cones contributing to overall slower release kinetics. Slow release in rods involves Ca2+-induced Ca2+ release (CICR). By impairing release from ribbons, we found that unlike cones where release occurs entirely at ribbon-style active zones, slow release from rods occurs mostly at ectopic, non-ribbon sites. To investigate the role of CICR in ribbon and non-ribbon release from rods, we used total internal reflection fluorescence microscopy (TIRFM) a...

  4. The permeability transition pore as a Ca2+ release channel: New answers to an old question

    Science.gov (United States)

    Bernardi, Paolo; von Stockum, Sophia

    2012-01-01

    Mitochondria possess a sophisticated array of Ca2+ transport systems reflecting their key role in physiological Ca2+ homeostasis. With the exception of most yeast strains, energized organelles are endowed with a very fast and efficient mechanism for Ca2+ uptake, the ruthenium red (RR)-sensitive mitochondrial Ca2+ uniporter (MCU); and one main mechanism for Ca2+ release, the RR-insensitive 3Na+–Ca2+ antiporter. An additional mechanism for Ca2+ release is provided by a Na+ and RR-insensitive release mechanism, the putative 3H+–Ca2+ antiporter. A potential kinetic imbalance is present, however, because the Vmax of the MCU is of the order of 1400 nmol Ca2+ mg−1 protein min−1 while the combined Vmax of the efflux pathways is about 20 nmol Ca2+ mg−1 protein min−1. This arrangement exposes mitochondria to the hazards of Ca2+ overload when the rate of Ca2+ uptake exceeds that of the combined efflux pathways, e.g. for sharp increases of cytosolic [Ca2+]. In this short review we discuss the hypothesis that transient opening of the Ca2+-dependent permeability transition pore may provide mitocondria with a fast Ca2+ release channel preventing Ca2+ overload. We also address the relevance of a mitochondrial Ca2+ release channel recently discovered in Drosophila melanogaster, which possesses intermediate features between the permeability transition pore of yeast and mammals. PMID:22513364

  5. The permeability transition pore as a Ca(2+) release channel: new answers to an old question.

    Science.gov (United States)

    Bernardi, Paolo; von Stockum, Sophia

    2012-07-01

    Mitochondria possess a sophisticated array of Ca(2+) transport systems reflecting their key role in physiological Ca(2+) homeostasis. With the exception of most yeast strains, energized organelles are endowed with a very fast and efficient mechanism for Ca(2+) uptake, the ruthenium red (RR)-sensitive mitochondrial Ca(2+) uniporter (MCU); and one main mechanism for Ca(2+) release, the RR-insensitive 3Na(+)-Ca(2+) antiporter. An additional mechanism for Ca(2+) release is provided by a Na(+) and RR-insensitive release mechanism, the putative 3H(+)-Ca(2+) antiporter. A potential kinetic imbalance is present, however, because the V(max) of the MCU is of the order of 1400nmol Ca(2+)mg(-1) proteinmin(-1) while the combined V(max) of the efflux pathways is about 20nmol Ca(2+)mg(-1) proteinmin(-1). This arrangement exposes mitochondria to the hazards of Ca(2+) overload when the rate of Ca(2+) uptake exceeds that of the combined efflux pathways, e.g. for sharp increases of cytosolic [Ca(2+)]. In this short review we discuss the hypothesis that transient opening of the Ca(2+)-dependent permeability transition pore may provide mitocondria with a fast Ca(2+) release channel preventing Ca(2+) overload. We also address the relevance of a mitochondrial Ca(2+) release channel recently discovered in Drosophila melanogaster, which possesses intermediate features between the permeability transition pore of yeast and mammals. PMID:22513364

  6. Comparative characterization of two intracellular Ca²⁺-release channels from the red flour beetle, Tribolium castaneum.

    Science.gov (United States)

    Liu, Yaping; Li, Chengjun; Gao, Jingkun; Wang, Wenlong; Huang, Li; Guo, Xuezhu; Li, Bin; Wang, Jianjun

    2014-10-21

    Ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP3Rs) are members of a family of tetrameric intracellular Ca(2+)-release channels (CRCs). While it is well known in mammals that RyRs and IP3Rs modulate multiple physiological processes, the roles of these two CRCs in the development and physiology of insects remain poorly understood. In this study, we cloned and functionally characterized RyR and IP3R cDNAs (named TcRyR and TcIP3R) from the red flour beetle, Tribolium castaneum. The composite TcRyR gene contains an ORF of 15,285 bp encoding a protein of 5,094 amino acid residues. The TcIP3R contains an 8,175 bp ORF encoding a protein of 2,724 amino acids. Expression analysis of TcRyR and TcIP3R revealed significant differences in mRNA expression levels among T. castaneum during different developmental stages. When the transcript levels of TcRyR were suppressed by RNA interference (RNAi), an abnormal folding of the adult hind wings was observed, while the RNAi-mediated knockdown of TcIP3R resulted in defective larval-pupal and pupal-adult metamorphosis. These results suggested that TcRyR is required for muscle excitation-contraction (E-C) coupling in T. castaneum, and that calcium release via IP3R might play an important role in regulating ecdysone synthesis and release during molting and metamorphosis in insects.

  7. Voltage-gated potassium channel Kvl.3 in rabbit ciliary epithelium regulates the membrane potential via coupling intracellular calcium

    Institute of Scientific and Technical Information of China (English)

    LI Yan-feng; ZHUO Ye-hong; BI Wei-na; BAI Yu-jing; LI Yan-na; WANG Zhi-jian

    2008-01-01

    Background The cell layer of the ciliary epithelium is responsible for aqueous humor secretion and maintenance.Ion channels play an important role in these processes.The main aim of this study was to determine whether the well-characterized members of the Kvl family (Kv1.3) contribute to the Kv currents in ciliary epithelium.Methods New Zealand White rabbits were maintained in a 12 hours light/dark cycle.Ciliary epithelium samples were isolated from the rabbits.We used Western blotting and immunocytochemistry to identify the expression and location of a voltage-gated potassium channel Kvl.3 in ciliary body epithelium.Membrane potential change after adding of Kv1.3 inhibitor margatoxin (MgTX) was observed with a fluorescence method.Results Western blotting and immunocytochemical studies showed that the Kv1.3 protein expressed in pigment ciliary epithelium and nonpigment ciliary epithelium,however it seemed to express more in the apical membrane of the nonpigmented epithelial cells.One nmol/L margatoxin,a specific inhibitor of Kv1.3 channels caused depolarization of the cultured nonpigmented epithelium (NPE) membrane potential.The cytosotic calcium increased after NPE cell depolarization,this increase of cytosolic calcium was partially blocked by 12.5 μmol/L dantrolene and 10 μmol/L nifedipine.These observations suggest that Kv1.3 channels modulate ciliary epithelium potential and effect calcium dependent mechanisms.Conclusion Kv1.3 channels contribute to K+ efflux at the membrane of rabbit ciliary epithelium.

  8. T-type calcium channels promote predictive homeostasis of input-output relations in thalamocortical neurons of lateral geniculate nucleus.

    Science.gov (United States)

    Hong, Su Z; Kim, Haram R; Fiorillo, Christopher D

    2014-01-01

    A general theory views the function of all neurons as prediction, and one component of this theory is that of "predictive homeostasis" or "prediction error." It is well established that sensory systems adapt so that neuronal output maintains sensitivity to sensory input, in accord with information theory. Predictive homeostasis applies the same principle at the cellular level, where the challenge is to maintain membrane excitability at the optimal homeostatic level so that spike generation is maximally sensitive to small gradations in synaptic drive. Negative feedback is a hallmark of homeostatic mechanisms, as exemplified by depolarization-activated potassium channels. In contrast, T-type calcium channels exhibit positive feedback that appears at odds with the theory. In thalamocortical neurons of lateral geniculate nucleus (LGN), T-type channels are capable of causing bursts of spikes with an all-or-none character in response to excitation from a hyperpolarized potential. This "burst mode" would partially uncouple visual input from spike output and reduce the information spikes convey about gradations in visual input. However, past observations of T-type-driven bursts may have resulted from unnaturally high membrane excitability. Here we have mimicked within rat brain slices the patterns of synaptic conductance that occur naturally during vision. In support of the theory of predictive homeostasis, we found that T-type channels restored excitability toward its homeostatic level during periods of hyperpolarization. Thus, activation of T-type channels allowed two retinal input spikes to cause one output spike on average, and we observed almost no instances in which output count exceeded input count (a "burst"). T-type calcium channels therefore help to maintain a single optimal mode of transmission rather than creating a second mode. More fundamentally our results support the general theory, which seeks to predict the properties of a neuron's ion channels and

  9. FM dyes enter via a store-operated calcium channel and modify calcium signaling of cultured astrocytes

    OpenAIRE

    Li, Dongdong; Hérault, Karine; Oheim, Martin; Ropert, Nicole

    2009-01-01

    The amphiphilic fluorescent styryl pyridinium dyes FM1-43 and FM4-64 are used to probe activity-dependent synaptic vesicle cycling in neurons. Cultured astrocytes can internalize FM1-43 and FM4-64 inside vesicles but their uptake is insensitive to the elevation of cytosolic calcium (Ca2+) concentration and the underlying mechanism remains unclear. Here we used total internal reflection fluorescence microscopy and pharmacological tools to study the mechanisms of FM4-64 uptake into cultured ast...

  10. Comparing Titanium Release from Ceramic Tiles using a waste material characterization test - Influence of Calcium and Organic Matter concentrations

    DEFF Research Database (Denmark)

    Heggelund, Laura Roverskov; Hansen, Steffen Foss; Astrup, Thomas Fruergaard;

    2015-01-01

    be deposited in landfills for construction and demolition waste or other types of landfills, depending on the local waste management system. Hence, the potential release of nano-Ti under landfill conditions is relevant to investigate. In this study we used a standard waste material characterization method...... waste material to the landfill leachate, it is expected that the calcium and organic matter content in the liquid will affect the stability of the nanoparticles. The concentration of calcium in the landfill percolate is expected to decrease the stability of the particles due to compression...... of the electric double layer surrounding the particle, causing increased particle agglomeration and settling. Natural organic matter might have both a stabilizing and destabilizing effect on the released nano-Ti particles depending on the concentration, since this will specifically influence the ability...

  11. Suppression of formalin-induced nociception by cilnidipine, a voltage-dependent calcium channel blocker.

    Science.gov (United States)

    Koganei, Hajime; Shoji, Masataka; Iwata, Seinosuke

    2009-10-01

    Cilnidipine is a 1,4-dihydropyridine-derived voltage-dependent calcium channel (VDCC) blocker and suppresses N-type VDCC currents in addition to L-type VDCC currents. An earlier investigation has suggested that intrathecally injected cilnidipine produces antinociception by blocking N-type VDCCs in mice. The present study using the rat formalin model examined antinociceptive effects of intrathecally and orally administered cilnidipine to elucidate a putative site of antinociception of cilnidipine, assess the efficacy of oral cilnidipine for pain relief, and clarify the mechanism(s) responsible for the antinociceptive effect of oral cilnidipine. Cilnidipine (whether intrathecal or oral) suppressed nociception in phases 1 and 2 of the formalin model. In addition, the potency of oral cilnidipine to suppress formalin-induced nociception in phase 2 was greater than that of oral gabapentin, a clinically available drug for treatment of neuropathic pain. Cilnidipine elicited antinociceptive effects without neurological side-effects including serpentine-like tail movement, whole body shaking, and allodynia. Such side-effects can be induced by higher doses of intrathecal ziconotide, a clinically available N-type VDCC blocker. In contrast, orally administered nifedipine, an L-type VDCC blocker, had no effect on either phase of formalin-induced nociception. These results suggest that cilnidipine acts on the spinal cord to produce antinociception and is efficacious for pain relief after oral administration with better safety profile than that of ziconotide. Furthermore, the failure of orally administered nifedipine to affect formalin-induced nociception raises the possibility that oral cilnidipine produces antinociception through, at least in part, spinal N-type VDCC blockade. PMID:19801830

  12. Lessons learned from a novel calcium-channel protagonist and person.

    Science.gov (United States)

    Dillon, Margaret

    2015-11-15

    A long time ago (circa 1976), David C. Triggle was Chair of the Department of Biochemical Pharmacology at S.U.N.Y. Buffalo where he led the faculty and staff in the education and mentoring of countless pharmacy and graduate students who passed through the hallowed halls of the University. Trained as a chemist, David spent his days synthesizing new and improved calcium channel blockers in a cramped, makeshift organic chemistry lab while a lab full of aspiring pharmacologists measured their effects on contractile responses of various smooth muscle preparations. I was a graduate student fortunate enough to land in David's laboratory, and thanks to him, I successfully navigated out with a Ph.D. in hand. That being said, his influence was less through his role as thesis advisor and more by the example he set in his simple, everyday life in Buffalo, N.Y: his love for - and dedication to - his family, his concern for the environment and his health, his perseverance in that tiny organic chemistry closet, his command of the English language, his unbridled honesty and cynicism, and his quiet pursuit of excellence. This article chronicles student life during that particular time period and provides a glimpse into David's unique personality and lifestyle that made him a role model to me and others. Interwoven is my own circuitous career path both before and after leaving S.U.N.Y. Buffalo that culminated in a productive career at the opposite end of the drug development process from where it all started in pharmacology. PMID:26206185

  13. Oxidized Low-density Lipoprotein (ox-LDL) Cholesterol Induces the Expression of miRNA-223 and L-type Calcium Channel Protein in Atrial Fibrillation

    Science.gov (United States)

    He, Fengping; Xu, Xin; Yuan, Shuguo; Tan, Liangqiu; Gao, Lingjun; Ma, Shaochun; Zhang, Shebin; Ma, Zhanzhong; Jiang, Wei; Liu, Fenglian; Chen, Baofeng; Zhang, Beibei; Pang, Jungang; Huang, Xiuyan; Weng, Jiaqiang

    2016-08-01

    Atrial fibrillation (AF) is the most common sustained arrhythmia causing high morbidity and mortality. While changing of the cellular calcium homeostasis plays a critical role in AF, the L-type calcium channel α1c protein has suggested as an important regulator of reentrant spiral dynamics and is a major component of AF-related electrical remodeling. Our computational modeling predicted that miRNA-223 may regulate the CACNA1C gene which encodes the cardiac L-type calcium channel α1c subunit. We found that oxidized low-density lipoprotein (ox-LDL) cholesterol significantly up-regulates both the expression of miRNA-223 and L-type calcium channel protein. In contrast, knockdown of miRNA-223 reduced L-type calcium channel protein expression, while genetic knockdown of endogenous miRNA-223 dampened AF vulnerability. Transfection of miRNA-223 by adenovirus-mediated expression enhanced L-type calcium currents and promoted AF in mice while co-injection of a CACNA1C-specific miR-mimic counteracted the effect. Taken together, ox-LDL, as a known factor in AF-associated remodeling, positively regulates miRNA-223 transcription and L-type calcium channel protein expression. Our results implicate a new molecular mechanism for AF in which miRNA-223 can be used as an biomarker of AF rheumatic heart disease.

  14. Oxidized Low-density Lipoprotein (ox-LDL) Cholesterol Induces the Expression of miRNA-223 and L-type Calcium Channel Protein in Atrial Fibrillation.

    Science.gov (United States)

    He, Fengping; Xu, Xin; Yuan, Shuguo; Tan, Liangqiu; Gao, Lingjun; Ma, Shaochun; Zhang, Shebin; Ma, Zhanzhong; Jiang, Wei; Liu, Fenglian; Chen, Baofeng; Zhang, Beibei; Pang, Jungang; Huang, Xiuyan; Weng, Jiaqiang

    2016-01-01

    Atrial fibrillation (AF) is the most common sustained arrhythmia causing high morbidity and mortality. While changing of the cellular calcium homeostasis plays a critical role in AF, the L-type calcium channel α1c protein has suggested as an important regulator of reentrant spiral dynamics and is a major component of AF-related electrical remodeling. Our computational modeling predicted that miRNA-223 may regulate the CACNA1C gene which encodes the cardiac L-type calcium channel α1c subunit. We found that oxidized low-density lipoprotein (ox-LDL) cholesterol significantly up-regulates both the expression of miRNA-223 and L-type calcium channel protein. In contrast, knockdown of miRNA-223 reduced L-type calcium channel protein expression, while genetic knockdown of endogenous miRNA-223 dampened AF vulnerability. Transfection of miRNA-223 by adenovirus-mediated expression enhanced L-type calcium currents and promoted AF in mice while co-injection of a CACNA1C-specific miR-mimic counteracted the effect. Taken together, ox-LDL, as a known factor in AF-associated remodeling, positively regulates miRNA-223 transcription and L-type calcium channel protein expression. Our results implicate a new molecular mechanism for AF in which miRNA-223 can be used as an biomarker of AF rheumatic heart disease. PMID:27488468

  15. ADVECTION AND DIFFUSION OF POISONOUS GAS CONTAMINANT RELEASED FROM BOTTOM SLUDGE IN OPEN CHANNEL

    Institute of Scientific and Technical Information of China (English)

    WU Zhou-hu

    2004-01-01

    In some cases, poisonous contaminants may be released from bottom sludge in open channels. The equation of advection and diffusion for the related problem was analyzed in this paper. The conditions for the definite solution to the equation were given. The analytic solution of poisonous gas concentration distribution was worked out. The reasonableness of this solution was discussed. The result is also of significance for other similar problems.

  16. CNTF-Treated Astrocyte Conditioned Medium Enhances Large-Conductance Calcium-Activated Potassium Channel Activity in Rat Cortical Neurons.

    Science.gov (United States)

    Sun, Meiqun; Liu, Hongli; Xu, Huanbai; Wang, Hongtao; Wang, Xiaojing

    2016-08-01

    Seizure activity is linked to astrocyte activation as well as dysfunctional cortical neuron excitability produced from changes in calcium-activated potassium (KCa) channel function. Ciliary neurotrophic factor-treated astrocyte conditioned medium (CNTF-ACM) can be used to investigate the peripheral effects of activated astrocytes upon cortical neurons. However, CNTF-ACM's effect upon KCa channel activity in cultured cortical neurons has not yet been investigated. Whole-cell patch clamp recordings were performed in rat cortical neurons to evaluate CNTF-ACM's effects upon charybdotoxin-sensitive large-conductance KCa (BK) channel currents and apamin-sensitive small-conductance KCa (SK) channel current. Biotinylation and RT-PCR were applied to assess CNTF-ACM's effects upon the protein and mRNA expression, respectively, of the SK channel subunits SK2 and SK3 and the BK channel subunits BKα1 and BKβ3. An anti-fibroblast growth factor-2 (FGF-2) monoclonal neutralizing antibody was used to assess the effects of the FGF-2 component of CNTF-ACM. CNTF-ACM significantly increased KCa channel current density, which was predominantly attributable to gains in BK channel activity (p  0.05). Blocking FGF-2 produced significant reductions in KCa channel current density (p > 0.05) as well as BKα1 and BKβ3 expression in CNTF-ACM-treated neurons (p > 0.05). CNTF-ACM significantly enhances BK channel activity in rat cortical neurons and that FGF-2 is partially responsible for these effects. CNTF-induced astrocyte activation results in secretion of neuroactive factors which may affect neuronal excitability and resultant seizure activity in mammalian cortical neurons. PMID:27097551

  17. Ryanodine modification of cardiac muscle responses to potassium-free solutions. Evidence for inhibition of sarcoplasmic reticulum calcium release

    OpenAIRE

    1983-01-01

    To test whether ryanodine blocks the release of calcium from the sarcoplasmic reticulum in cardiac muscle, we examined its effects on the aftercontractions and transient depolarizations or transient inward currents developed by guinea pig papillary muscles and voltage-clamped calf cardiac Purkinje fibers in potassium-free solutions. Ryanodine (0.1-1.0 microM) abolished or prevented aftercontractions and transient depolarizations by the papillary muscles without affecting any of the other sequ...

  18. Dopamine release in organotypic cultures of foetal mouse mesencephalon: effects of depolarizing agents, pargyline, nomifensine, tetrodotoxin and calcium

    DEFF Research Database (Denmark)

    Larsen, Trine R; Rossen, Sine; Gramsbergen, Jan B

    2008-01-01

    endogenous DA release (assessed by high-performance liquid chromatography) in organotypic cultures of foetal mouse (E12) midbrain following single or multiple challenges (1-h incubations) with high K(+) or veratridine in the presence or absence of pargyline, nomifensine, calcium and/or tetrodotoxin (TTX......Organotypic mesencephalic cultures provide an attractive in vitro alternative to study development of the nigrostriatal system and pathophysiological mechanisms related to Parkinson's disease. However, dopamine (DA) release mechanisms have been poorly characterized in such cultures. We report here...

  19. The two-pore channel TPCN2 mediates NAADP-dependent Ca(2+)-release from lysosomal stores.

    Science.gov (United States)

    Zong, Xiangang; Schieder, Michael; Cuny, Hartmut; Fenske, Stefanie; Gruner, Christian; Rötzer, Katrin; Griesbeck, Oliver; Harz, Hartmann; Biel, Martin; Wahl-Schott, Christian

    2009-09-01

    Second messenger-induced Ca(2+)-release from intracellular stores plays a key role in a multitude of physiological processes. In addition to 1,4,5-inositol trisphosphate (IP(3)), Ca(2+), and cyclic ADP ribose (cADPR) that trigger Ca(2+)-release from the endoplasmatic reticulum (ER), nicotinic acid adenine dinucleotide phosphate (NAADP) has been identified as a cellular metabolite that mediates Ca(2+)-release from lysosomal stores. While NAADP-induced Ca(2+)-release has been found in many tissues and cell types, the molecular identity of the channel(s) conferring this release remained elusive so far. Here, we show that TPCN2, a novel member of the two-pore cation channel family, displays the basic properties of native NAADP-dependent Ca(2+)-release channels. TPCN2 transcripts are widely expressed in the body and encode a lysosomal protein forming homomers. TPCN2 mediates intracellular Ca(2+)-release after activation with low-nanomolar concentrations of NAADP while it is desensitized by micromolar concentrations of this second messenger and is insensitive to the NAADP analog nicotinamide adenine dinucleotide phosphate (NADP). Furthermore, TPCN2-mediated Ca(2+)-release is almost completely abolished when the capacity of lysosomes for storing Ca(2+) is pharmacologically blocked. By contrast, TPCN2-specific Ca(2+)-release is unaffected by emptying ER-based Ca(2+) stores. In conclusion, these findings indicate that TPCN2 is a major component of the long-sought lysosomal NAADP-dependent Ca(2+)-release channel.

  20. Immunoglobulin Fc gamma receptor promotes immunoglobulin uptake, immunoglobulin-mediated calcium increase, and neurotransmitter release in motor neurons

    Science.gov (United States)

    Mohamed, Habib A.; Mosier, Dennis R.; Zou, Ling L.; Siklos, Laszlo; Alexianu, Maria E.; Engelhardt, Jozsef I.; Beers, David R.; Le, Wei-dong; Appel, Stanley H.

    2002-01-01

    Receptors for the Fc portion of immunoglobulin G (IgG; FcgammaRs) facilitate IgG uptake by effector cells as well as cellular responses initiated by IgG binding. In earlier studies, we demonstrated that amyotrophic lateral sclerosis (ALS) patient IgG can be taken up by motor neuron terminals and transported retrogradely to the cell body and can alter the function of neuromuscular synapses, such as increasing intracellular calcium and spontaneous transmitter release from motor axon terminals after passive transfer. In the present study, we examined whether FcgammaR-mediated processes can contribute to these effects of ALS patient immunoglobulins. F(ab')(2) fragments (which lack the Fc portion) of ALS patient IgG were not taken up by motor axon terminals and were not retrogradely transported. Furthermore, in a genetically modified mouse lacking the gamma subunit of the FcR, the uptake of whole ALS IgG and its ability to enhance intracellular calcium and acetylcholine release were markedly attenuated. These data suggest that FcgammaRs appear to participate in IgG uptake into motor neurons as well as IgG-mediated increases in intracellular calcium and acetylcholine release from motor axon terminals. Copyright 2002 Wiley-Liss, Inc.

  1. Regulation of Calcium Channels and Exocytosis in Mouse Adrenal Chromaffin Cells by Prostaglandin EP3 Receptors

    Science.gov (United States)

    Jewell, Mark L.; Breyer, Richard M.

    2011-01-01

    Prostaglandin (PG) E2 controls numerous physiological functions through a family of cognate G protein-coupled receptors (EP1–EP4). Targeting specific EP receptors might be therapeutically useful and reduce side effects associated with nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors that block prostanoid synthesis. Systemic immune challenge and inflammatory cytokines have been shown to increase expression of the synthetic enzymes for PGE2 in the adrenal gland. Catecholamines and other hormones, released from adrenal chromaffin cells in response to Ca2+ influx through voltage-gated Ca2+ channels, play central roles in homeostatic function and the coordinated stress response. However, long-term elevation of circulating catecholamines contributes to the pathogenesis of hypertension and heart failure. Here, we investigated the EP receptor(s) and cellular mechanisms by which PGE2 might modulate chromaffin cell function. PGE2 did not alter resting intracellular [Ca2+] or the peak amplitude of nicotinic acetylcholine receptor currents, but it did inhibit CaV2 voltage-gated Ca2+ channel currents (ICa). This inhibition was voltage-dependent and mediated by pertussis toxin-sensitive G proteins, consistent with a direct Gβγ subunit-mediated mechanism common to other Gi/o-coupled receptors. mRNA for all four EP receptors was detected, but using selective pharmacological tools and EP receptor knockout mice, we demonstrated that EP3 receptors mediate the inhibition of ICa. Finally, changes in membrane capacitance showed that Ca2+-dependent exocytosis was reduced in parallel with ICa. To our knowledge, this is the first study of EP receptor signaling in mouse chromaffin cells and identifies a molecular mechanism for paracrine regulation of neuroendocrine function by PGE2. PMID:21383044

  2. Calcium channel blocking activity of calycosin, a major active component of Astragali Radix, on rat aorta

    Institute of Scientific and Technical Information of China (English)

    Xiu-li WU; Yin-ye WANG; Jun CHENG; Yu-ying ZHAO

    2006-01-01

    Aim: To investigate the vasoactivity of calycosin, a major active component of Astragali Radix. Methods: Experiments were performed on isolated rat thoracic aortic rings pre-contracted with phenylephrine (PHE) or KC1. Results: Calycosin produced a concentration-dependent relaxation on the tissue pre-contracted using PHE with 4.46±0.13 of pD2 and 95.85%±2.67% of Emax; or using KC1 with 4.27±0.05 of pD2 and 99.06%±2.15% of Emax, and displaced downwards the concentration-response curves of aortic rings to PHE or KC1. The relaxant effect of calycosin on denuded endothelium aortic rings was the same as on intact endothelium aortic rings, and its vasorelaxant effect was not influenced by L-NAME or indomethacin. In Ca2+-free solution, calycosin (30 μmol/L) did not have an effect on PHE (1×10-6 mol/L)-induced aortic ring contraction. The effects of calycosin and nifedipine where somewhat different; calycosin decreased aortic ring contractions induced by the two agonists, but nifedipine displayed a more potent inhibitory effect on KC1-induced contractions than on PHE-induced contractions, and the vascular relaxing effects of calycosin and nifidipine were additive on PHE-induced contraction but not KC1-induced. Conclusion: Calycosin is a vasorelaxant. Its action is endothelium-independent and is unrelated to intracellular Ca2+release. It is a noncompetitive Ca2+ channel blocker. The effect of calycosin on Ca2+ channel blockade may be different from that of dihydropyridines. This study demonstrated a novel pharmacological activity of calycosin, and supplied a theoretic foundation for Astragali Radix application.

  3. Effect of cutter type on sediment pollutants release in channel dredging

    Science.gov (United States)

    Yu, Y. R.; Chen, Y.; Dong, M. M.; Yang, B. L.

    2016-08-01

    Dredging activities are often used to maintain existing navigation channels. However’ traditional dredging equipment inevitably leads to sediment resuspension and nutrient loading in water. In this work’ the existing cutter used for dredging was transformed environmentally to reduce the release amount of sediment pollutants’ and to avoid the formation of secondary pollution to water bodies. Simulated tests with a general cutter’ a spiral cutter’ along with a general and spiral cutter equipped with the anti-diffusion device were conducted respectively in this study. The change of pollutants concentration in overlying water was examined. The environmental performance of each different structure cutter was comparatively analysed as well. The result revealed that in channel dredging with a spiral cutter’ the release amount of sediment pollutants was less than with a general cutter’ and that a general/spiral cutter equipped with the anti-diffusion device could effectively reduce the release amount of sediment contaminants’ particularly the release of the nitrogen nutrient during the 1h after the dredging treatment. The best transformation scheme for a cutter suction dredger (CSD) in its environmental-protection function may be: a spiral cutter equipped with the anti-diffusion device.

  4. Somatic and germline CACNA1D calcium channel mutations in aldosterone-producing adenomas and primary aldosteronism

    Science.gov (United States)

    Scholl, Ute I.; Goh, Gerald; Stölting, Gabriel; de Oliveira, Regina Campos; Choi, Murim; Overton, John D.; Fonseca, Annabelle L.; Korah, Reju; Starker, Lee F.; Kunstman, John W.; Prasad, Manju L.; Hartung, Erum A.; Mauras, Nelly; Benson, Matthew R.; Brady, Tammy; Shapiro, Jay R.; Loring, Erin; Nelson-Williams, Carol; Libutti, Steven K.; Mane, Shrikant; Hellman, Per; Westin, Gunnar; Åkerström, Göran; Björklund, Peyman; Carling, Tobias; Fahlke, Christoph; Hidalgo, Patricia; Lifton, Richard P.

    2013-01-01

    Adrenal aldosterone-producing adenomas (APAs) constitutively produce the salt-retaining hormone aldosterone and are a common cause of severe hypertension. Recurrent mutations in the potassium channel KCNJ5 that result in cell depolarization and Ca2+ influx cause ~40% of these tumors1. We found five somatic mutations (four altering glycine 403, one altering isoleucine 770) in CACNA1D, encoding a voltage-gated calcium channel, among 43 non-KCNJ5-mutant APAs. These mutations lie in S6 segments that line the channel pore. Both result in channel activation at less depolarized potentials, and glycine 403 mutations also impair channel inactivation. These effects are inferred to cause increased Ca2+ influx, the sufficient stimulus for aldosterone production and cell proliferation in adrenal glomerulosa2. Remarkably, we identified de novo mutations at the identical positions in two children with a previously undescribed syndrome featuring primary aldosteronism and neuromuscular abnormalities. These findings implicate gain of function Ca2+ channel mutations in aldosterone-producing adenomas and primary aldosteronism. PMID:23913001

  5. Effects of low-dose ionising radiation on pituitary adenoma: is there a role for L-type calcium channel?

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Marcella Araugio; Santos, Raquel Gouvea dos [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN), Belo Horizonte, MG (Brazil). Lab. de Radiobiologia]. E-mail: santosr@cdtn.br

    2005-10-15

    Pituitary adenomas constitute about 6-18% of brain tumours in adults. Activation of voltage gated calcium currents can account for growth hormone over secretion in some GH-secreting pituitary adenomas that produce an acromegaly appearance and increase mortality. Ca{sup 2+} ions, as mediators of intracellular signalling, are crucial for the development of apoptosis. However, the role of [Ca{sup 2+}] in the development of apoptosis is ambiguous. In this study, the effects of low-dose ionising gamma radiation ({sup 60} Co) on rat pituitary adenoma cells survival and proliferation and the role of calcium channels on the apoptosis radio-induced were evaluated. Doses as low as 3 Gy were found to inhibit GH3 cell proliferation. Even though there was a significant number of live cells,168 hours following irradiation, they were not able to proliferate. The results indicate that the blockade of extracellular calcium influx through these channels does not interfere in the radiation-induced apoptosis in GH3 cells. (author)

  6. Design, synthesis, and pharmacological evaluation of haloperidol derivatives as novel potent calcium channel blockers with vasodilator activity.

    Directory of Open Access Journals (Sweden)

    Yicun Chen

    Full Text Available Several haloperidol derivatives with a piperidine scaffold that was decorated at the nitrogen atom with different alkyl, benzyl, or substituted benzyl moieties were synthesized at our laboratory to establish a library of compounds with vasodilator activity. Compounds were screened for vasodilatory activity on isolated thoracic aorta rings from rats, and their quantitative structure-activity relationships (QSAR were examined. Based on the result of QSAR, N-4-tert-butyl benzyl haloperidol chloride (16c was synthesized and showed the most potent vasodilatory activity of all designed compounds. 16c dose-dependently inhibited the contraction caused by the influx of extracellular Ca(2+ in isolated thoracic aorta rings from rats. It concentration-dependently attenuated the calcium channel current and extracellular Ca(2+ influx, without affecting the intracellular Ca(2+ mobilization, in vascular smooth muscle cells from rats. 16c, possessing the N-4-tert-butyl benzyl piperidine structure, as a novel calcium antagonist, may be effective as a calcium channel blocker in cardiovascular disease.

  7. Calcium in plant cells

    Directory of Open Access Journals (Sweden)

    V. V. Schwartau

    2014-04-01

    connect ion conformationally rearranged, thus passing the signal through the chain of intermediaries. The most important function of calcium is its participation in many cell signaling pathways. Channels, pumps, gene expression, synthesis of alkaloids, protective molecules, NO etc. respond to changes in [Ca2+]cyt, while transductors are represented by a number of proteins. The universality of calcium is evident in the study in connection with other signaling systems, such as NO, which is involved in the immune response and is able to control the feedback activity of protein activators channels, producing nitric oxide. Simulation of calcium responses can determine the impact of key level and their regulation, and also depends on the type of stimulus and the effector protein that specifically causes certain changes. Using spatiotemporal modeling, scientists showed that the key components for the formation of Ca2+ bursts are the internal and external surfaces of the nucleus membrane. The research was aimed at understanding of the mechanisms of influence of Ca2+-binding components on Ca2+ oscillations. The simulation suggests the existence of a calcium depot EPR with conjugated lumen of the nucleus which releases its contents to nucleoplasm. With these assumptions, the mathematical model was created and confirmed experimentally. It describes the oscillation of nuclear calcium in root hairs of Medicago truncatula at symbiotic relationship of plants and fungi (rhizobia. Calcium oscillations are present in symbiotic relationships of the cortical layer of plant root cells. Before penetration of bacteria into the cells, slow oscillations of Ca2+ are observed, but with their penetration into the cells the oscillation frequency increases. These processes take place by changing buffer characteristics of the cytoplasm caused by signals from microbes, such as Nod-factor available after penetration of bacteria through the cell wall. Thus, the basic known molecular mechanisms for

  8. 钙通道阻滞剂的镇痛作用及其机制研究进展%Research progress of analgesic effect and its mechanisms of calcium channel blockers

    Institute of Scientific and Technical Information of China (English)

    尹睛; 屠伟峰; 陶元祥; 马亚平; 康旭

    2013-01-01

    Background Voltage-dependent calcium channels (VDCCs) are involved in the mechanism of occurrence and maintenance of pain,calcium channel blockers show well analgesic effect.Objective To review and summarize the analgesic effect and its mechanisms of main types of calcium channel blockers.Content Neurons which can feel noxious stimuli distributed in dorsal root ganglia (DRG) and spinal cord dorsal horn have a large number of VDCCs,can regulate depolarization-induced influx of Ca2+,thus affect the release of glutamate and substance P and other pain-related neurotransmitter.Calcium channel blockers,such as Ziconotide,have a clear analgesic effect and are not easy to form tolerance and cause respiratory depression,but the routes of administration are limited,and therapeutic window narrow.Trend In order to develop more convenient and safe drugs,and to provide more choices for the clinical use,the analgesic effect of calcium channel blockers needs more further research and discussion.%背景 电压依赖性钙通道(voltage dependent calcium channels,VDCCs)参与了疼痛的发生及维持机制,钙通道阻滞剂在临床前及临床试验中显示出良好的镇痛作用. 目的 对主要的钙通道阻滞剂的镇痛作用及其机制进行回顾和总结. 内容 背根神经节(dorsal root ganglia,DRG)及脊髓背角感受伤害性刺激的神经元上有大量VDCCs分布,可调控去极化诱导的Ca2+内流,从而影响谷氨酸和P物质等与疼痛有关的神经递质释放.齐考诺肽等钙通道阻滞剂具有明确的镇痛作用,且不易形成耐受性及引起呼吸抑制,但给药途径受限,治疗窗狭窄. 趋向 钙通道阻滞剂的镇痛作用还需进行更深入的研究和探讨,从而开发更加安全方便的新型药物,为临床用药提供更多选择.

  9. [Clinical efficacy of calcium channel blockers slow the third generation of lercanidipine in the treatment of patients with arterial hypertension and metabolic disorders (review)].

    Science.gov (United States)

    Tabidze, G A; Gezeli, T D; Tsibadze, T A; Dolidze, N M

    2015-02-01

    Arterial hypertension is the most common risk factor in patients with metabolic disorders. In the selection of antihypertensive therapy it is necessary to consider not only the anti-hypertensive and organoprotective effects of drugs and their metabolic effects, which has prognostic value. Calcium antaginists, along. Lercanidipine related to the third generation dihydripyridine calcium antagonist, has been much more selective for the so-called slow calcium channels of vascular smooth muscle cells, which is associated with a good hypertensive, organo and metabolic action. Combination therapy with an ACE inhibitor and a calcium channel blocker is also a justified tactic for the management of patients with high-risk cardiovascular and metabolic disorders. Attention is paid new fixed combinations, including angiotensin converting enzyme inhibitors and calcium antagonists.

  10. Ultrastructure of cardiac muscle in reptiles and birds: optimizing and/or reducing the probability of transmission between calcium release units.

    Science.gov (United States)

    Perni, Stefano; Iyer, V Ramesh; Franzini-Armstrong, Clara

    2012-06-01

    It is known that cardiac myocytes contain three categories of calcium release units (CRUs) all bearing arrays of RyR2: peripheral couplings, constituted of an association of the junctional SR (jSR) with the plasmalemma; dyads, associations between jSR and T tubules; internal extended junctional jSR (EjSR)/corbular jSR that is not associated with plasmalemma/T tubules. The bird hearts, even if fast beating (e.g., in finch and hummingbird) have no T tubules, despite fiber sizes comparable to those of mammalian ventricle, but are rich in EjSR/corbular SR. The heart of small lizard also lacks T tubule, but it has only peripheral couplings and compensates for lack of internal CRUs by the small diameter of its cells. We have extended previous information on chicken heart to finch and lizard by establishing a spatial relationship between RyR2 clusters in jSR of peripheral couplings and clusters of intra-membrane particles identifiable as voltage sensitive calcium channels (CaV1.2) in the adjacent plasmalemma. This provides the structural basis for initiation of the heart beat in all three species. Further we evaluated the distances separating peripheral couplings from each other and between EjSR/corbular SR sites within the bird muscles in all three hearts. The distances suggest that peripheral coupling sites are most likely to act independently of each other and that a calcium wave-front propagation from one internal CRU site to the other across the level of the Z line, may be marginally successful in the chicken, but certainly very effective in the finch. PMID:22576825

  11. Characterization of [125I]omega-conotoxin binding to brain N calcium channels and (-)[3H] desmethoxyverapamil binding to novel calcium channels in osteoblast-like osteosarcoma cells

    International Nuclear Information System (INIS)

    This dissertation provides molecular evidence for a diversity of Ca2+ channels in neuronal and non-neuronal tissues. First, I demonstrated specific, reversible, saturable binding sites for omega [125I]conotoxin GVIA (omega[125I]CTX) in rat brain and rabbit sympathetic ganglion. Omega [125I]CTX binding has a unique pharmacology, ion selectivity, and anatomical distribution in rat brain. Omega [125I]CTX binding was solubilized, retaining an appropriate pharmacology and ion selectivity. Omega[125I]CTX binding may be associated with a Ca2+ channel because the K/sub D/ of omega [125I]CTX is similar to the IC50 of inhibition of depolarization-induced 45Ca2+ flux into rat brain synaptosomes. Specific (-)[3H]desmethoxyverapamil ((-)[3H]DMV) binding sites were demonstrated on osteoblast-like osteosarcoma cell membranes

  12. Comparative evaluation of the calcium release from mineral trioxide aggregate and its mixture with glass ionomer cement in different proportions and time intervals – An in vitro study

    Directory of Open Access Journals (Sweden)

    Surbhi Sawhney

    2015-10-01

    Conclusions: Adding GIC to improve the setting time and handling properties of the MTA powder can be detrimental to the calcium-releasing ability of the resultant mixture, depending on the proportion of GIC added. Adding MTA and GIC at a proportion of 2:1 by volume did not impact calcium release from the mixture. These findings should be verified through further clinical studies.

  13. Studies of the voltage-sensitive calcium channels in smooth muscle, neuronal, and cardiac tissues using 1,4-dihydropyridine calcium channel antagonists and activators

    International Nuclear Information System (INIS)

    This study describes the investigation of the voltage-sensitive Ca+ channels in vascular and intestinal smooth muscle, chick neural retina cells and neonatal rat cardiac myocytes using 1,4-dihydropyridine Ca2+ channel antagonists and activators. In rat aorta, the tumor promoting phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) produced Ca2+-dependent contractile responses. The responses to TPA were blocked by the Ca2+ channel antagonists. The effects of the enantiomers of Bay K 8644 and 202-791 were characterized in both rat tail artery and guinea pig ileal longitudinal smooth muscle preparations using pharmacologic and radioligand binding assays. The (S)-enantiomers induced contraction and potentiated the responses to K+ depolarization. The (R)-enantiomers inhibited the tension responses to K+. All the enantiomers inhibited specific [3H]nitrendipine binding. The pharmacologic activities of both activator and antagonist ligands correlated on a 1:1 basis with the binding affinities. In chick neural retina cells the (S)-enantiomers of Bay K 8644 and 202-791 enhanced Ca2+ influx. In contrast, the (R)-enantiomers inhibited Ca2+ influx. The enantiomers of Bay K 8644 and 202-791 inhibited specific [3H]PN 200-110 binding competitively. Binding of 1,4-dihydropyridines was characterized in neonatal rat heart cells

  14. Endothelin-1 induces intracellular [Ca2+] increase via Ca2+ influx through the L-type Ca2+ channel, Ca2+-induced Ca2+ release and a pathway involving ETA receptors, PKC, PKA and AT1 receptors in cardiomyocytes

    Institute of Scientific and Technical Information of China (English)

    ZENG QingHua; LI XingTing; ZHONG GuoGan; ZHANG WenJie; SUN ChengWen

    2009-01-01

    Using fura-2-acetoxymethyl eater (AM) fluorescence imaging and patch clamp techniques, we found that endothelin-1 (ET-1) significantly elevated the intracellular calcium level ([Ca2+]1) in a dose-dependent manner and activated the L-type Ca2+ channel in cardiomyocytes isolated from rats.The effect of ET-1 on [Ca2+]1 elevation was abolished in the presence of the ETA receptor blocker BQ123,but was not affected by the ETa receptor blocker BQ788. ET-1-induced an increase in [Ca2+]1, which was inhibited 46.7% by pretreatment with a high concentration of ryanodine (10 μmol/L), a blocker of the ryanodine receptor. The ET-1-induced [Ca2+]i increase was also inhibited by the inhibltors of protein kinase A (PKA), protein kinase C (PKC) and angiotensin type 1 receptor (AT1 receptor). We found that ET-1 induced an enhancement of the amplitude of the whole cell L-type Ca2+ channel current and an Increase of open-state probability (NPo) of an L-type single Ca2+ channel. BQ123 completely blocked the ET-1-induced increase in calcium channel open-state probability. In this study we demonstrated that ET-1 regulates calcium overload through a series of mechanisms that include L-type Ca2+ channel activation and Ca2+-induced Ca2+ release (CICR). ETa receptors, PKC, PKA and AT1 receptors may also contribute to this pathway.

  15. Endothelin-1 induces intracellular [Ca2+] increase via Ca2+ influx through the L-type Ca2+ channel, Ca2+-induced Ca2+ release and a pathway involving ETA receptors, PKC, PKA and AT1 receptors in cardiomyocytes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Using fura-2-acetoxymethyl ester (AM) fluorescence imaging and patch clamp techniques, we found that endothelin-1 (ET-1) significantly elevated the intracellular calcium level ([Ca2+]i) in a dose-dependent manner and activated the L-type Ca2+ channel in cardiomyocytes isolated from rats. The effect of ET-1 on [Ca2+]i elevation was abolished in the presence of the ETA receptor blocker BQ123, but was not affected by the ETB receptor blocker BQ788. ET-1-induced an increase in [Ca2+]i, which was inhibited 46.7% by pretreatment with a high concentration of ryanodine (10 μmol/L), a blocker of the ryanodine receptor. The ET-1-induced [Ca2+]i increase was also inhibited by the inhibitors of protein kinase A (PKA), protein kinase C (PKC) and angiotensin type 1 receptor (AT1 receptor). We found that ET-1 induced an enhancement of the amplitude of the whole cell L-type Ca2+ channel current and an increase of open-state probability (NPo) of an L-type single Ca2+ channel. BQ123 completely blocked the ET-1-induced increase in calcium channel open-state probability. In this study we demonstrated that ET-1 regulates calcium overload through a series of mechanisms that include L-type Ca2+ channel activation and Ca2+-induced Ca2+ release (CICR). ETA receptors, PKC, PKA and AT1 receptors may also contribute to this pathway.

  16. High glucose enhances transient receptor potential channel canonical type 6-dependent calcium influx in human platelets via phosphatidylinositol 3-kinase-dependent pathway

    DEFF Research Database (Denmark)

    Liu, Daoyan; Maier, Alexandra; Scholze, Alexandra;

    2008-01-01

    Transient receptor potential canonical type 6 (TRPC6) channels mediating 1-oleoyl-2-acetyl-sn-glycerol (OAG)-induced calcium entry have been identified on human platelets. In the present study we tested the hypothesis that hyperglycemia increases the expression of TRPC6 channels....

  17. Potentiation of Opioid-Induced Analgesia by L-Type Calcium Channel Blockers: Need for Clinical Trial in Cancer Pain

    Directory of Open Access Journals (Sweden)

    S Basu Ray

    2008-01-01

    Full Text Available Previous reports indicate that the analgesic effect of opioids is due to both closure of specific voltage-gated calcium channels (N- and P/Q-types and opening of G protein-coupled inwardly rectifying potassium channels (GIRKs in neurons concerned with transmission of pain. However, administration of opioids leads to unacceptable levels of side effects, particularly at high doses. Thus, current research is directed towards simultaneously targeting other voltage-gated calcium channels (VGCCs like the L-type VGCCs or even other cell signaling mechanisms, which would aug-ment opioid-mediated analgesic effect without a concurrent increase in the side effects. Unfortunately, the results of these studies are often conflicting considering the different experimental paradigms (variable drug selection and their doses and also the specific pain test used for studying analgesia adopted by researchers. The present review focuses on some of the interesting findings regarding the analgesic effect of Opioids + L-VGCC blockers and suggests that time has come for a clinical trial of this combination of drugs in the treatment of cancer pain.

  18. Mechanism of store-operated calcium entry

    Indian Academy of Sciences (India)

    Devkanya Dutta

    2000-12-01

    Activation of receptors coupled to the phospholipase C/IP3 signalling pathway results in a rapid release of calcium from its intracellular stores, eventually leading to depletion of these stores. Calcium store depletion triggers an influx of extracellular calcium across the plasma membrane, a mechanism known as the store-operated calcium entry or capacitative calcium entry. Capacitative calcium current plays a key role in replenishing calcium stores and activating various physiological processes. Despite considerable efforts, very little is known about the molecular nature of the capacitative channel and the signalling pathway that activates it. This review summarizes our current knowledge about store operated calcium entry and suggests possible hypotheses for its mode of activation.

  19. Specific association of growth-associated protein 43 with calcium release units in skeletal muscles of lower vertebrates

    Directory of Open Access Journals (Sweden)

    G.A. Caprara

    2014-10-01

    Full Text Available Growth-associated protein 43 (GAP43, is a strictly conserved protein among vertebrates implicated in neuronal development and neurite branching. Since GAP43 structure contains a calmodulin-binding domain, this protein is able to bind calmodulin and gather it nearby membrane network, thus regulating cytosolic calcium and consequently calcium-dependent intracellular events. Even if for many years GAP43 has been considered a neuronal-specific protein, evidence from different laboratories described its presence in myoblasts, myotubes and adult skeletal muscle fibers. Data from our laboratory showed that GAP43 is localized between calcium release units (CRUs and mitochondria in mammalian skeletal muscle suggesting that, also in skeletal muscle, this protein can be a key player in calcium/calmodulin homeostasis. However, the previous studies could not clearly distinguish between a mitochondrion- or a triad-related positioning of GAP43. To solve this question, the expression and localization of GAP43 was studied in skeletal muscle of Xenopus and Zebrafish known to have triads located at the level of the Z-lines and mitochondria not closely associated with them. Western blotting and immunostaining experiments revealed the expression of GAP43 also in skeletal muscle of lower vertebrates (like amphibians and fishes, and that the protein is localized closely to the triad junction. Once more, these results and GAP43 structural features, support an involvement of the protein in the dynamic intracellular Ca2+ homeostasis, a common conserved role among the different species.

  20. Neuronal calcium sensor-1 deletion in the mouse decreases motivation and dopamine release in the nucleus accumbens.

    Science.gov (United States)

    Ng, Enoch; Varaschin, Rafael K; Su, Ping; Browne, Caleb J; Hermainski, Joanna; Le Foll, Bernard; Pongs, Olaf; Liu, Fang; Trudeau, Louis-Eric; Roder, John C; Wong, Albert H C

    2016-03-15

    Calcium sensors detect intracellular calcium changes and interact with downstream targets to regulate many functions. Neuronal Calcium Sensor-1 (NCS-1) or Frequenin is widely expressed in the nervous system, and involved in neurotransmission, synaptic plasticity and learning. NCS-1 interacts with and regulates dopamine D2 receptor (D2R) internalization and is implicated in disorders like schizophrenia and substance abuse. However, the role of NCS-1 in behaviors dependent on dopamine signaling in the striatum, where D2R is most highly expressed, is unknown. We show that Ncs-1 deletion in the mouse decreases willingness to work for food. Moreover, Ncs-1 knockout mice have significantly lower activity-dependent dopamine release in the nucleus accumbens core in acute slice recordings. In contrast, food preference, responding for conditioned reinforcement, ability to represent changes in reward value, and locomotor response to amphetamine are not impaired. These studies identify novel roles for NCS-1 in regulating activity-dependent striatal dopamine release and aspects of motivated behavior.

  1. AHR-16303B, a novel antagonist of 5-HT2 receptors and voltage-sensitive calcium channels

    International Nuclear Information System (INIS)

    In vivo and in vitro methods were used to characterize AHR-16303B, a novel compound with antagonistic action at 5-HT2 receptors and voltage-sensitive calcium channels. The 5-HT2 receptor-antagonistic properties of AHR-16303B were demonstrated by inhibition of (a) [3H]ketanserin binding to rat cerebral cortical membranes (IC50 = 165 nM); (b) 5-hydroxytryptamine (5-HT)-induced foot edema in rats (minimum effective dose, (MED) = 0.32 mg/kg orally, p.o.); (c) 5-HT-induced vasopressor responses in spontaneously hypertensive rats (SHR) (ID50 = 0.18 mg/kg intravenously (i.v.), 1.8 mg/kg p.o.), (d) 5-HT-induced antidiuresis in rats (MED = 1 mg/kg p.o.), and (e) platelet aggregation induced by 5-HT + ADP (IC50 = 1.5 mM). The calcium antagonist properties of AHR-16303B were demonstrated by inhibition of (a) [3H]nimodipine binding to voltage-sensitive calcium channels on rabbit skeletal muscle membranes (IC50 = 15 nM), (b) KCl-stimulated calcium flux into cultured PC12 cells (IC50 = 81 nM), and (c) CaCl2-induced contractions of rabbit thoracic aortic strips (pA2 = 8.84). AHR-16303B had little or no effect on binding of radioligands to dopamine2 (DA2) alpha 1, alpha 2, H1, 5-HT1 alpha, beta 2, muscarinic M1, or sigma opioid receptors; had no effect on 5-HT3 receptor-mediated vagal bradycardia; and had only minor negative inotropic, chronotropic, and dromotropic effects on isolated guinea pig atria. In conscious SHR, 30 mg/kg p.o. AHR-16303B completely prevented the vasopressor responses to i.v. 5-HT, and decreased blood pressure (BP) by 24% 3 h after dosing

  2. Combinations of physiologic estrogens with xenoestrogens alter calcium and kinase responses, prolactin release, and membrane estrogen receptor trafficking in rat pituitary cells

    Directory of Open Access Journals (Sweden)

    Watson Cheryl S

    2010-10-01

    Full Text Available Abstract Background Xenoestrogens such as alkylphenols and the structurally related plastic byproduct bisphenol A have recently been shown to act potently via nongenomic signaling pathways and the membrane version of estrogen receptor-α. Though the responses to these compounds are typically measured individually, they usually contaminate organisms that already have endogenous estrogens present. Therefore, we used quantitative medium-throughput screening assays to measure the effects of physiologic estrogens in combination with these xenoestrogens. Methods We studied the effects of low concentrations of endogenous estrogens (estradiol, estriol, and estrone at 10 pM (representing pre-development levels, and 1 nM (representing higher cycle-dependent and pregnancy levels in combinations with the same levels of xenoestrogens in GH3/B6/F10 pituitary cells. These levels of xenoestrogens represent extremely low contamination levels. We monitored calcium entry into cells using Fura-2 fluorescence imaging of single cells. Prolactin release was measured by radio-immunoassay. Extracellular-regulated kinase (1 and 2 phospho-activations and the levels of three estrogen receptors in the cell membrane (ERα, ERβ, and GPER were measured using a quantitative plate immunoassay of fixed cells either permeabilized or nonpermeabilized (respectively. Results All xenoestrogens caused responses at these concentrations, and had disruptive effects on the actions of physiologic estrogens. Xenoestrogens reduced the % of cells that responded to estradiol via calcium channel opening. They also inhibited the activation (phosphorylation of extracellular-regulated kinases at some concentrations. They either inhibited or enhanced rapid prolactin release, depending upon concentration. These latter two dose-responses were nonmonotonic, a characteristic of nongenomic estrogenic responses. Conclusions Responses mediated by endogenous estrogens representing different life stages are

  3. The Polarized Effect of Intracellular Calcium on the Renal Epithelial Sodium Channel Occurs as a Result of Subcellular Calcium Signaling Domains Maintained by Mitochondria.

    Science.gov (United States)

    Thai, Tiffany L; Yu, Ling; Galarza-Paez, Laura; Wu, Ming Ming; Lam, Ho Yin Colin; Bao, Hui Fang; Duke, Billie Jeanne; Al-Khalili, Otor; Ma, He-Ping; Liu, Bingchen; Eaton, Douglas C

    2015-11-27

    The renal epithelial sodium channel (ENaC) provides regulated sodium transport in the distal nephron. The effects of intracellular calcium ([Ca(2+)]i) on this channel are only beginning to be elucidated. It appears from previous studies that the [Ca(2+)]i increases downstream of ATP administration may have a polarized effect on ENaC, where apical application of ATP and the subsequent [Ca(2+)]i increase have an inhibitory effect on the channel, whereas basolateral ATP and [Ca(2+)]i have a stimulatory effect. We asked whether this polarized effect of ATP is, in fact, reflective of a polarized effect of increased [Ca(2+)]i on ENaC and what underlying mechanism is responsible. We began by performing patch clamp experiments in which ENaC activity was measured during apical or basolateral application of ionomycin to increase [Ca(2+)]i near the apical or basolateral membrane, respectively. We found that ENaC does indeed respond to increased [Ca(2+)]i in a polarized fashion, with apical increases being inhibitory and basolateral increases stimulating channel activity. In other epithelial cell types, mitochondria sequester [Ca(2+)]i, creating [Ca(2+)]i signaling microdomains within the cell that are dependent on mitochondrial localization. We found that mitochondria localize in bands just beneath the apical and basolateral membranes in two different cortical collecting duct principal cell lines and in cortical collecting duct principal cells in mouse kidney tissue. We found that inhibiting mitochondrial [Ca(2+)]i uptake destroyed the polarized response of ENaC to [Ca(2+)]i. Overall, our data suggest that ENaC is regulated by [Ca(2+)]i in a polarized fashion and that this polarization is maintained by mitochondrial [Ca(2+)]i sequestration. PMID:26451045

  4. Lung adenocarcinoma with Lambert–Eaton myasthenic syndrome indicated by voltage-gated calcium channel: a case report

    Directory of Open Access Journals (Sweden)

    Arai Hiromasa

    2012-09-01

    Full Text Available Abstract Introduction Lambert–Eaton myasthenic syndrome is a rare disorder and it is known as a paraneoplastic neurological syndrome. Small cell lung cancer often accompanies this syndrome. Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma is extremely rare; there are only a few reported cases worldwide. Case presentation A 75-year-old Japanese man with a past history of chronic rheumatoid arthritis and Sjögren syndrome was diagnosed with Lambert–Eaton myasthenic syndrome by electromyography and serum anti-P/Q-type voltage-gated calcium channel antibody level preceding the diagnosis of lung cancer. A chest computed tomography to screen for malignant lesions revealed an abnormal shadow in the lung. Although a histopathological examination by bronchoscopic study could not reveal the malignancy, lung cancer was mostly suspected after the results of a chest computed tomography and [18F]-fluorodeoxyglucose positron emission tomography. An intraoperative diagnosis based on the frozen section obtained by tumor biopsy was adenocarcinoma so the patient underwent a lobectomy of the right lower lobe and lymph node dissection with video-assisted thoracoscopic surgery. The permanent pathological examination was the same as the frozen diagnosis (pT2aN1M0: Stage IIa: TNM staging 7th edition. Immunohistochemistry revealed that most of the cancer cells were positive for P/Q-type voltage-gated calcium channel. Conclusions Our case is a rare combination of Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma, rheumatoid arthritis and Sjögren syndrome, and to the best of our knowledge it is the first report that indicates the presence of voltage-gated calcium channel in lung adenocarcinoma by immunostaining.

  5. Antineoplastic Effect of Calcium Channel Blocker-Verapamil and 5-Fluorouracil Intraperitoneal Chemotherapy on Hepatocarcinoma-Bearing Rats

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Objective To study the antineoplastic effect of the calcium channel blocker verapamil and 5-fluorouracil intraperitoneal chemotherapy on hepatocarcinoma-bearing rats,and examine the action between calcium channel blockers and cytotoxic drugs. Methods We adopted the method of subcapsular implantation of carcinoma tissues of walker-256 in the left liver lobe as a model of liver carcinoma-bearing rats.All experimental animals were divided into four groups.On the sixth day post implantation,in group A (control group) 6ml of saline was injected intraperitoneally once a day for 3 days.In group B(single chemotherapy group) 6ml of 5-Fu 75 mg/kg was injected intraperitoneally once a day for 3 days.In group C(combination of treatment group)both 5-Fu(75mg/kg) and verapamil (25mg/kg) were administered simultaneously as in A and B.In group D(simple verapamil group)only 6ml of verapamil(25mg/kg)was administered as above. Results Compared with groups A, B and D,The volume of cancer and the contents of liver cancer DNA and protein were significantly reduced.The rates of inhibiting cancer(89.9% in group C and 35.4% in group B)were significantly increased in groupC. Group C had significantly long survival time compared to groups A, B and D(P<0.05).By light microscopy, a number of focal necroses were found in cancer tissue in group C.Conclusion Calcium channel blockers can enhance the antineoplastic effect of 5-Fu intraperitonea chemotherapy to liver cancer;The use of verapamil can not increase the toxicity of 5-Fu.

  6. Magnesium Sensitizes Slow Vacuolar Channels to Physiological Cytosolic Calcium and Inhibits Fast Vacuolar Channels in Fava Bean Guard Cell Vacuoles.

    Science.gov (United States)

    Pei; Ward; Schroeder

    1999-11-01

    Vacuolar ion channels in guard cells play important roles during stomatal movement and are regulated by many factors including Ca(2+), calmodulin, protein kinases, and phosphatases. We report that physiological cytosolic and luminal Mg(2+) levels strongly regulate vacuolar ion channels in fava bean (Vicia faba) guard cells. Luminal Mg(2+) inhibited fast vacuolar (FV) currents with a K(i) of approximately 0.23 mM in a voltage-dependent manner at positive potentials on the cytoplasmic side. Cytosolic Mg(2+) at 1 mM also inhibited FV currents. Furthermore, in the absence of cytosolic Mg(2+), cytosolic Ca(2+) at less than 10 µM did not activate slow vacuolar (SV) currents. However, when cytosolic Mg(2+) was present, submicromolar concentrations of cytosolic Ca(2+) activated SV currents with a K(d) of approximately 227 nM, suggesting a synergistic Mg(2+)-Ca(2+) effect. The activation potential of SV currents was shifted toward physiological potentials in the presence of cytosolic Mg(2+) concentrations. The direction of SV currents could also be changed from outward to both outward and inward currents. Our data predict a model for SV channel regulation, including a cytosolic binding site for Ca(2+) with an affinity in the submicromolar range and a cytosolic low-affinity Mg(2+)-Ca(2+) binding site. SV channels are predicted to contain a third binding site on the vacuolar luminal side, which binds Ca(2+) and is inhibitory. In conclusion, cytosolic Mg(2+) sensitizes SV channels to physiological cytosolic Ca(2+) elevations. Furthermore, we propose that cytosolic and vacuolar Mg(2+) concentrations ensure that FV channels do not function as a continuous vacuolar K(+) leak, which would prohibit stomatal opening. PMID:10557247

  7. Caffeine Modulates Vesicle Release and Recovery at Cerebellar Parallel Fibre Terminals, Independently of Calcium and Cyclic AMP Signalling.

    Directory of Open Access Journals (Sweden)

    Katharine L Dobson

    Full Text Available Cerebellar parallel fibres release glutamate at both the synaptic active zone and at extrasynaptic sites-a process known as ectopic release. These sites exhibit different short-term and long-term plasticity, the basis of which is incompletely understood but depends on the efficiency of vesicle release and recycling. To investigate whether release of calcium from internal stores contributes to these differences in plasticity, we tested the effects of the ryanodine receptor agonist caffeine on both synaptic and ectopic transmission.Whole cell patch clamp recordings from Purkinje neurons and Bergmann glia were carried out in transverse cerebellar slices from juvenile (P16-20 Wistar rats.Caffeine caused complex changes in transmission at both synaptic and ectopic sites. The amplitude of postsynaptic currents in Purkinje neurons and extrasynaptic currents in Bergmann glia were increased 2-fold and 4-fold respectively, but paired pulse ratio was substantially reduced, reversing the short-term facilitation observed under control conditions. Caffeine treatment also caused synaptic sites to depress during 1 Hz stimulation, consistent with inhibition of the usual mechanisms for replenishing vesicles at the active zone. Unexpectedly, pharmacological intervention at known targets for caffeine--intracellular calcium release, and cAMP signalling--had no impact on these effects.We conclude that caffeine increases release probability and inhibits vesicle recovery at parallel fibre synapses, independently of known pharmacological targets. This complex effect would lead to potentiation of transmission at fibres firing at low frequencies, but depression of transmission at high frequency connections.

  8. Emerging roles of calcium-activated K channels and TRPV4 channels in lung oedema and pulmonary circulatory collapse

    DEFF Research Database (Denmark)

    Simonsen, Ulf; Wandall-Frostholm, Christine; Oliván-Viguera, Aida;

    2016-01-01

    endothelial/epithelial barrier functions and vascular integrity, while KCa3.1 channels provide the driving force required for Cl(-) and water transport in some cells and most secretory epithelia. The three conditions, increased pulmonary venous pressure caused by left heart disease, high inflation pressure......, fluid extravasation, hemorrhage, pulmonary circulatory collapse, and cardiac arrest in vivo. These data identify KCa3.1 channels as crucial molecular components in downstream TRPV4-signal transduction and as a potential target for the prevention of undesired fluid extravasation, vasodilatation...

  9. EDRF [endothelium-derived relaxing factor]-release and Ca++-channel blockage by Magnolol, an antiplatelet agent isolated from Chinese herb Magnolia officinalis, in rat thoracic aorta

    International Nuclear Information System (INIS)

    Magnolol is an antiplatelet agent isolated from Chinese herb Magnolia officinalis. It inhibited norepinephrine-induced phasic and tonic contractions in rat thoracic aorta. At the plateau of the NE-induced tonic contraction, addition of magnolol caused two phases (fast and slow) of relaxation. These two relaxations were concentration-dependent, and were not inhibited by indomethacin. The fast relaxation was completely antagonized by hemoglobin and methylene blue, and disappeared in de-endothelialized aorta while the slow relaxation was not affected by the above treatments. Magnolol also inhibited high potassium-induced, calcium-dependent contraction of rat aorta in a concentration-dependent manner. 45Ca++ influx induced by high potassium or NE was markedly inhibited by magnolol. Cyclic GMP, but not PGI2, was increased by magnolol in intact, but not in de-endothelialized aorta. It is concluded that magnolol relaxed vascular smooth muscle by releasing endothelium-derived relaxing factor (EDRF) and by inhibiting calcium influx through voltage-gated calcium channels

  10. P/Q-type and T-type voltage-gated calcium channels are involved in the contraction of mammary and brain blood vessels from hypertensive patients

    DEFF Research Database (Denmark)

    Thuesen, A D; Lyngsø, K S; Rasmussen, L;

    2016-01-01

    AIM: Calcium channel blockers are widely used in cardiovascular diseases. Besides L-type channels, T- and P/Q-type calcium channels are involved in the contraction of human renal blood vessels. It was hypothesized that T- and P/Q-type channels are involved in the contraction of human brain...... and mammary blood vessels. METHODS: Internal mammary arteries from bypass surgery patients and cerebral arterioles from patients with brain tumours with and without hypertension were tested in a myograph and perfusion set-up. PCR and immunohistochemistry were performed on isolated blood vessels. RESULTS...... labelling of mammary and cerebral arteries revealed the presence of Cav 2.1 in endothelial and smooth muscle cells. Cav 3.1 was also detected in mammary arteries. CONCLUSION: P/Q- and T-type Cav are present in human internal mammary arteries and in cerebral penetrating arterioles. P/Q- and T-type calcium...

  11. New insights into the activation mechanism of store-operated calcium channels:roles of STIM and Orai

    Institute of Scientific and Technical Information of China (English)

    Rui-wei GUO; Lan HUANG

    2008-01-01

    The activation of Ca2+ entry through store-operated channels by agonists that deplete Ca2+ from the endoplasmic reticulum (ER)is a ubiquitous signaling mechanism,the molecular basis of which has remained elusive for the past two decades.Store-operated Ca2+-release-activated Ca2+(CRAC)channels constitute the sole pathway for Ca2+ entry following antigen-receptor engagement.In a set of breakthrough studies over the past two years,stromal interaction molecule l(STIM1,tbe ER Ca2+ sensor) and Orail(a pore-forming subunit of the CRAC channel)have been identified.Here we review these recent studies and the insights they provide into the mechanism of store-operated Ca2+ channels(SOCCs).

  12. Metabotropic glutamate receptor 6 signaling enhances TRPM1 calcium channel function and increases melanin content in human melanocytes

    OpenAIRE

    Devi, Sulochana; Markandeya, Yogananda; Maddodi, Nityanand; Dhingra, Anuradha; Vardi, Noga; Ravi C Balijepalli; Setaluri, Vijayasaradhi

    2013-01-01

    Mutations in TRPM1, a calcium channel expressed in retinal bipolar cells and epidermal melanocytes, cause complete congenital stationary night blindness with no discernible skin phenotype. In the retina, TRPM1 activity is negatively coupled to metabotropic glutamate receptor 6 (mGluR6) signaling through Gαo and TRPM1 mutations result in the loss of responsiveness of TRPM1 to mGluR6 signaling. Here, we show that human melanocytes express mGluR6 and treatment of melanocytes with L-AP4, a type I...

  13. The mystery is solved-CatSper is the principal calcium channel activated by progesterone in human spermatozoa

    Institute of Scientific and Technical Information of China (English)

    Christopher LR Barratt

    2011-01-01

    @@ Aremarkable advance in sperm physiology has recently been published in Nature.Two groups using patch clamping techniques on human sperm have solved a mystery about the sperm cell that has puzzled both andrologists and those involved in non-genomic cellular signalling for over 20 years.In these papers, Lishko1 and Strunker2 independently demonstrate that the universal characteristic effect of progesterone on sperm-a rapid influx of calcium-is via a sperm-specific channel CatSper.

  14. Role of Calcium-activated Potassium Channels in Atrial Fibrillation Pathophysiology and Therapy.

    Science.gov (United States)

    Diness, Jonas G; Bentzen, Bo H; Sørensen, Ulrik S; Grunnet, Morten

    2015-11-01

    Small-conductance Ca(2+)-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels because they might constitute a relatively atrial-selective target. This review will give a general introduction to SK channels followed by their proposed function in the heart under normal and pathophysiological conditions. It is revealed how antiarrhythmic effects can be obtained by SK channel inhibition in a number of species in situations of atrial fibrillation. On the contrary, the beneficial effects of SK channel inhibition in situations of heart failure are questionable and still needs investigation. The understanding of cardiac SK channels is rapidly increasing these years, and it is hoped that this will clarify whether SK channel inhibition has potential as a new anti-atrial fibrillation principle. PMID:25830485

  15. Role of Calcium-activated Potassium Channels in Atrial Fibrillation Pathophysiology and Therapy.

    Science.gov (United States)

    Diness, Jonas G; Bentzen, Bo H; Sørensen, Ulrik S; Grunnet, Morten

    2015-11-01

    Small-conductance Ca(2+)-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels because they might constitute a relatively atrial-selective target. This review will give a general introduction to SK channels followed by their proposed function in the heart under normal and pathophysiological conditions. It is revealed how antiarrhythmic effects can be obtained by SK channel inhibition in a number of species in situations of atrial fibrillation. On the contrary, the beneficial effects of SK channel inhibition in situations of heart failure are questionable and still needs investigation. The understanding of cardiac SK channels is rapidly increasing these years, and it is hoped that this will clarify whether SK channel inhibition has potential as a new anti-atrial fibrillation principle.

  16. Calcium signaling in taste cells.

    Science.gov (United States)

    Medler, Kathryn F

    2015-09-01

    The sense of taste is a common ability shared by all organisms and is used to detect nutrients as well as potentially harmful compounds. Thus taste is critical to survival. Despite its importance, surprisingly little is known about the mechanisms generating and regulating responses to taste stimuli. All taste responses depend on calcium signals to generate appropriate responses which are relayed to the brain. Some taste cells have conventional synapses and rely on calcium influx through voltage-gated calcium channels. Other taste cells lack these synapses and depend on calcium release to formulate an output signal through a hemichannel. Beyond establishing these characteristics, few studies have focused on understanding how these calcium signals are formed. We identified multiple calcium clearance mechanisms that regulate calcium levels in taste cells as well as a calcium influx that contributes to maintaining appropriate calcium homeostasis in these cells. Multiple factors regulate the evoked taste signals with varying roles in different cell populations. Clearly, calcium signaling is a dynamic process in taste cells and is more complex than has previously been appreciated. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

  17. LKB1 Regulates Mitochondria-Dependent Presynaptic Calcium Clearance and Neurotransmitter Release Properties at Excitatory Synapses along Cortical Axons.

    Directory of Open Access Journals (Sweden)

    Seok-Kyu Kwon

    2016-07-01

    Full Text Available Individual synapses vary significantly in their neurotransmitter release properties, which underlie complex information processing in neural circuits. Presynaptic Ca2+ homeostasis plays a critical role in specifying neurotransmitter release properties, but the mechanisms regulating synapse-specific Ca2+ homeostasis in the mammalian brain are still poorly understood. Using electrophysiology and genetically encoded Ca2+ sensors targeted to the mitochondrial matrix or to presynaptic boutons of cortical pyramidal neurons, we demonstrate that the presence or absence of mitochondria at presynaptic boutons dictates neurotransmitter release properties through Mitochondrial Calcium Uniporter (MCU-dependent Ca2+ clearance. We demonstrate that the serine/threonine kinase LKB1 regulates MCU expression, mitochondria-dependent Ca2+ clearance, and thereby, presynaptic release properties. Re-establishment of MCU-dependent mitochondrial Ca2+ uptake at glutamatergic synapses rescues the altered neurotransmitter release properties characterizing LKB1-null cortical axons. Our results provide novel insights into the cellular and molecular mechanisms whereby mitochondria control neurotransmitter release properties in a bouton-specific way through presynaptic Ca2+ clearance.

  18. LKB1 Regulates Mitochondria-Dependent Presynaptic Calcium Clearance and Neurotransmitter Release Properties at Excitatory Synapses along Cortical Axons

    Science.gov (United States)

    Kwon, Seok-Kyu; Sando, Richard; Maximov, Anton; Polleux, Franck

    2016-01-01

    Individual synapses vary significantly in their neurotransmitter release properties, which underlie complex information processing in neural circuits. Presynaptic Ca2+ homeostasis plays a critical role in specifying neurotransmitter release properties, but the mechanisms regulating synapse-specific Ca2+ homeostasis in the mammalian brain are still poorly understood. Using electrophysiology and genetically encoded Ca2+ sensors targeted to the mitochondrial matrix or to presynaptic boutons of cortical pyramidal neurons, we demonstrate that the presence or absence of mitochondria at presynaptic boutons dictates neurotransmitter release properties through Mitochondrial Calcium Uniporter (MCU)-dependent Ca2+ clearance. We demonstrate that the serine/threonine kinase LKB1 regulates MCU expression, mitochondria-dependent Ca2+ clearance, and thereby, presynaptic release properties. Re-establishment of MCU-dependent mitochondrial Ca2+ uptake at glutamatergic synapses rescues the altered neurotransmitter release properties characterizing LKB1-null cortical axons. Our results provide novel insights into the cellular and molecular mechanisms whereby mitochondria control neurotransmitter release properties in a bouton-specific way through presynaptic Ca2+ clearance. PMID:27429220

  19. Activation of delta-opioid receptors inhibits neuronal-like calcium channels and distal steps of Ca(2+)-dependent secretion in human small-cell lung carcinoma cells.

    Science.gov (United States)

    Sher, E; Cesare, P; Codignola, A; Clementi, F; Tarroni, P; Pollo, A; Magnelli, V; Carbone, E

    1996-06-01

    Human small-cell lung carcinoma (SCLC) cells express neuronal-like voltage-operated calcium channels (VOCCs) and release mitogenic hormones such as serotonin (5-HT). Opioid peptides, on the other hand, have been shown to reduce SCLC cell proliferation by an effective autocrine pathway. Here we show that in GLC8 SCLC cells, only delta-opioid receptor subtype mRNA is expressed. Consistently, the selective delta-opioid agonist [D-Pen2-Pen5]-enkephalin (DPDPE), but not mu and kappa agonists, potently and dose-dependently inhibits high-threshold (HVA) VOCCs in these cells. As in peripheral neurons, this modulation is largely voltage-dependent, mediated by pertussis toxin (PTX)-sensitive G-proteins, cAMP-independent, and mainly affecting N-type VOCCs. With the same potency and selectivity, DPDPE also antagonizes the Ca(2+)-dependent release of [3H]serotonin ([3H]5-HT) from GLC8 cells. However, DPDPE inhibits not only the depolarization-induced release, but also the Ca(2+)-dependent secretion induced by thapsigargin or ionomycin. This suggests that besides inhibiting HVA VOCCs, opioids also exert a direct depressive action on the secretory apparatus in GLC8 cells. This latter effect also is mediated by a PTX-sensitive G-protein but, contrary to VOCC inhibition, it can be reversed by elevations of cAMP levels. These results show for the first time that opioids effectively depress both Ca2+ influx and Ca(2+)-dependent hormone release in SCLC cells by using multiple modulatory pathways. It can be speculated that the two mechanisms may contribute to the opioid antimitogenic action on lung neuroendocrine carcinoma cells. PMID:8642411

  20. Role of calcium-activated potassium channels with small conductance in bradykinin-induced vasodilation of porcine retinal arterioles

    DEFF Research Database (Denmark)

    Dalsgaard, Thomas; Kroigaard, Christel; Bek, Toke;

    2009-01-01

    PURPOSE: Endothelial dysfunction and impaired vasodilation may be involved in the pathogenesis of retinal vascular diseases. In the present study, the mechanisms underlying bradykinin vasodilation were examined and whether calcium-activated potassium channels of small (SK(Ca)) and intermediate (IK......(Ca)) conductance are involved in regulation of endothelium-dependent vasodilation in retinal arterioles was investigated. METHODS: Porcine retinal arterioles (diameter approximately 112 microm, N = 119) were mounted in microvascular myographs for isometric tension recordings. The arterioles were contracted with...... the thromboxane analogue, U46619, and concentration-response curves were constructed for bradykinin and a novel opener of SK(Ca) and IK(Ca) channels, NS309. RESULTS: In U46619-contracted arterioles, bradykinin and NS309 induced concentration-dependent relaxations. In vessels without endothelium...

  1. Preparation and characterization of nano-sized calcium carbonate as controlled release pesticide carrier for validamycin against Rhizoctonia solani

    International Nuclear Information System (INIS)

    Nano-sized calcium carbonate (nano-CC) was studied in terms of acting as a carrier for a pesticide. Nano-CC was prepared by reaction of calcium chloride and sodium carbonate by the reversed-phase microemulsion method and then loaded with the pesticide validamycin. The resulting material was characterized by X-ray diffraction analysis and scanning electron microscopy. The loading efficiency, sustained-release performance, germicidal efficacy, and stability also were investigated. The size of the loaded nano-CC can be adjusted to between 50 to 200 nm by varying the water/surfactant molar ratio from 30/1 to 10/1, and the loading efficiency can be increased to about 20% by increasing the size of the nano-CC. The material displayed better germicidal efficacy against Rhizoctonia solani compared to conventional technical validamycin after about 7 days, and the time of the release of validamycin was extended to 2 weeks. Given the loading efficiency, stability, sustained-release performance and good environmental compatibility of the material, the method for its preparation may be extended to other hydrophilic pesticide. (author)

  2. Protein kinase A modulation of CaV1.4 calcium channels.

    Science.gov (United States)

    Sang, Lingjie; Dick, Ivy E; Yue, David T

    2016-01-01

    The regulation of L-type Ca(2+) channels by protein kinase A (PKA) represents a crucial element within cardiac, skeletal muscle and neurological systems. Although much work has been done to understand this regulation in cardiac CaV1.2 Ca(2+) channels, relatively little is known about the closely related CaV1.4 L-type Ca(2+) channels, which feature prominently in the visual system. Here we find that CaV1.4 channels are indeed modulated by PKA phosphorylation within the inhibitor of Ca(2+)-dependent inactivation (ICDI) motif. Phosphorylation of this region promotes the occupancy of calmodulin on the channel, thus increasing channel open probability (PO) and Ca(2+)-dependent inactivation. Although this interaction seems specific to CaV1.4 channels, introduction of ICDI1.4 to CaV1.3 or CaV1.2 channels endows these channels with a form of PKA modulation, previously unobserved in heterologous systems. Thus, this mechanism may not only play an important role in the visual system but may be generalizable across the L-type channel family. PMID:27456671

  3. Protein kinase A modulation of CaV1.4 calcium channels

    Science.gov (United States)

    Sang, Lingjie; Dick, Ivy E.; Yue, David T.

    2016-07-01

    The regulation of L-type Ca2+ channels by protein kinase A (PKA) represents a crucial element within cardiac, skeletal muscle and neurological systems. Although much work has been done to understand this regulation in cardiac CaV1.2 Ca2+ channels, relatively little is known about the closely related CaV1.4 L-type Ca2+ channels, which feature prominently in the visual system. Here we find that CaV1.4 channels are indeed modulated by PKA phosphorylation within the inhibitor of Ca2+-dependent inactivation (ICDI) motif. Phosphorylation of this region promotes the occupancy of calmodulin on the channel, thus increasing channel open probability (PO) and Ca2+-dependent inactivation. Although this interaction seems specific to CaV1.4 channels, introduction of ICDI1.4 to CaV1.3 or CaV1.2 channels endows these channels with a form of PKA modulation, previously unobserved in heterologous systems. Thus, this mechanism may not only play an important role in the visual system but may be generalizable across the L-type channel family.

  4. Apo-states of calmodulin and CaBP1 control CaV1 voltage-gated calcium channel function through direct competition for the IQ domain

    Science.gov (United States)

    Findeisen, Felix; Rumpf, Christine; Minor, Daniel L.

    2013-01-01

    In neurons, binding of calmodulin (CaM) or calcium-binding protein 1 (CaBP1) to the CaV1 (L-type) voltage-gated calcium channel IQ domain endows the channel with diametrically opposed properties. CaM causes calcium-dependent inactivation (CDI) and limits calcium entry, whereas CaBP1 blocks CDI and allows sustained calcium influx. Here, we combine isothermal titration calorimetry (ITC) with cell-based functional measurements and mathematical modeling to show that these calcium sensors behave in a competitive manner that is explained quantitatively by their apo-state binding affinities for the IQ domain. This competition can be completely blocked by covalent tethering of CaM to the channel. Further, we show that Ca2+/CaM has a sub-picomolar affinity for the IQ domain that is achieved without drastic alteration of calcium binding properties. The observation that the apo-forms of CaM and CaBP1 compete with each other demonstrates a simple mechanism for direct modulation of CaV1 function and suggests a means by which excitable cells may dynamically tune CaV activity. PMID:23811053

  5. Discrepancy in calcium release from the sarcoplasmic reticulum and intracellular acidic stores for the protection of the heart against ischemia/reperfusion injury.

    Science.gov (United States)

    Khalaf, Aseel; Babiker, Fawzi

    2016-09-01

    We and others have demonstrated a protective effect of pacing postconditioning (PPC) against ischemia/reperfusion (I/R) injury. However, the mechanisms underlying this protection are not completely clear. In the present study, we evaluated the effects of calcium release from the sarcoplasmic reticulum (SR) and the novel intracellular acidic stores (AS). Isolated rat hearts (n = 6 per group) were subjected to coronary occlusion followed by reperfusion using a modified Langendorff system. Cardiac hemodynamics and contractility were assessed using a data acquisition program, and cardiac injury was evaluated by creatine kinase (CK) and lactate dehydrogenase (LDH) levels. Hearts were subjected to 30 min of regional ischemia, produced by ligation of the left anterior descending (LAD) coronary artery, followed by 30 min of reperfusion. The hearts were also subjected to PPC (3 cycles of 30 s of left ventricle (LV) pacing alternated with 30 s of right atrium (RA) pacing) and/or were treated during reperfusion with agonists or antagonists of release of calcium from SR or AS. PPC significantly (P < 0.05) normalized LV, contractility, and coronary vascular dynamics and significantly (P < 0.001) decreased heart enzyme levels compared to the control treatments. The blockade of SR calcium release resulted in a significant (P < 0.01) recovery in LV function and contractility and a significant reduction in CK and LDH levels (P < 0.01) when applied alone or in combination with PPC. Interestingly, the release of calcium from AS alone or in combination with PPC significantly improved LV function and contractility (P < 0.05) and significantly decreased the CK and LDH levels (P < 0.01) compared to the control treatments. An additive effect was produced when agonism of calcium release from AS or blockade of calcium release from the SR was combined with PPC. Calcium release from AS and blockade of calcium release from the SR protect the heart against I

  6. Functional properties of the CaV1.2 calcium channel activated by calmodulin in the absence of alpha2delta subunits.

    Science.gov (United States)

    Ravindran, Arippa; Kobrinsky, Evgeny; Lao, Qi Zong; Soldatov, Nikolai M

    2009-01-01

    Voltage-activated CaV1.2 calcium channels require association of the pore-forming alpha1C subunit with accessory CaVbeta and alpha2delta subunits. Binding of a single calmodulin (CaM) to alpha1C supports Ca2+-dependent inactivation (CDI). The human CaV1.2 channel is silent in the absence of CaVbeta and/or alpha2delta. Recently, we found that coexpression of exogenous CaM (CaMex) supports plasma membrane targeting, gating facilitation and CDI of the channel in the absence of CaVbeta. Here we discovered that CaMex and its Ca2+-insensitive mutant (CaM1234) rendered active alpha1C/CaVbeta channel in the absence of alpha2delta. Coexpression of CaMex with alpha1C and beta2d in calcium-channel-free COS-1 cells recovered gating of the channel and supported CDI. Voltage-dependence of activation was shifted by approximately +40 mV to depolarization potentials. The calcium current reached maximum at +40 mV (20 mM Ca2+) and exhibited approximately 3 times slower activation and 5 times slower inactivation kinetics compared to the wild-type channel. Furthermore, both CaMex and CaM1234 accelerated recovery from inactivation and induced facilitation of the calcium current by strong depolarization prepulse, the properties absent from the human vascular/neuronal CaV1.2 channel. The data suggest a previously unknown action of CaM that in the presence of CaVbeta; translates into activation of the alpha2delta-deficient calcium channel and alteration of its properties. PMID:19106618

  7. "Synthesis and smooth muscle Calcium channel antagonist effect of Alkyl, Aminoalkyl 1,4-Dihydro-2,6-Dimethyl-4-Nitroimidazole-3,5 Pyridine Dicarboxylates "

    Directory of Open Access Journals (Sweden)

    Miri R

    2001-08-01

    Full Text Available The discovery that 1,4-dihydropyridine (DHP class of calcium channel antagonist inhibits the Ca+² influx represented a major therapeutic advance in the treatment of cardiovascular diseases such as hypertension, angina pectoris and other spastic smooth muscle disorders. A novel class of calcium channel antagonist of flunarizine containing arylpiperazinyl moiety has recently been reported. It was therefore of interest to determine the effect that selected C-3 substituents contained amino alkyl and arylpiperazine, in conjunction with a C-4 1-methyl-5-nitro-2-imidazolyl substituents on calcium channel antagonist activity. The unsymmetrical analogues were prepared by a procedure reported by Meyer in which 1-methyl-5-nitro-imidazol-2-carboxaldehyde was reacted with acetoacetic esters and alkyl 3-aminocrotonate. In vitro calcium channel antagonist activities were determined by the use of high K+ contraction of guinea pig ileal longitudinal smooth muscle. All compounds exhibited comparable calcium channel antagonist activity (IC50=10^-9 to 10^-11 M against reference drug nifedipine (IC50=2.75±0.36 x 10^-10 M.

  8. Types of voltage—dependent calcium channels involved in high potassium depolarization—induced amylase secretion in the exocrine pancreatic tumour cell line AR4—2J

    Institute of Scientific and Technical Information of China (English)

    CUIZONGJIE

    1998-01-01

    In the perifused fura-2 loaded exocrine pancreatic acinar cell line AR4-2J pulses of high potassium induced repetitive increases in intracellular calcium,Attached cells when stimulated with high potassium secreted large amount of amylase.High potassium-induced secretion was dependent both on the concentration of potassium and duration of stimulation.High potassium induced increases in intracellular calcium were inhibited by voltage-dependent calcium channel anatagonists with an order of potency as follows:nifedipine>ω-agatoxin IVA>ω-conotoxin GVIA.In contrast,the L-type calcium channel anatagonist nifedipine almost completely inhibited potassium-induced amylase secretion,whereas the N-type channel antagonist ω-conotoxin GVIA was without effect.The P-type channel antagonist ω-agatoxin IVA had a small inhibitory effect,but this inhibition was not significant at the level of amylase secretion.In conclusion,the AR4-2J cell line posesses different voltage-dependent calcium channels(L,P,N)with the L-type predominantly involved in depolarization induced amylase secretion.

  9. Three dimensional neuronal cell cultures more accurately model voltage gated calcium channel functionality in freshly dissected nerve tissue.

    Directory of Open Access Journals (Sweden)

    Yinzhi Lai

    Full Text Available It has been demonstrated that neuronal cells cultured on traditional flat surfaces may exhibit exaggerated voltage gated calcium channel (VGCC functionality. To gain a better understanding of this phenomenon, primary neuronal cells harvested from mice superior cervical ganglion (SCG were cultured on two dimensional (2D flat surfaces and in three dimensional (3D synthetic poly-L-lactic acid (PLLA and polystyrene (PS polymer scaffolds. These 2D- and 3D-cultured cells were compared to cells in freshly dissected SCG tissues, with respect to intracellular calcium increase in response to high K(+ depolarization. The calcium increases were identical for 3D-cultured and freshly dissected, but significantly higher for 2D-cultured cells. This finding established the physiological relevance of 3D-cultured cells. To shed light on the mechanism behind the exaggerated 2D-cultured cells' functionality, transcriptase expression and related membrane protein distributions (caveolin-1 were obtained. Our results support the view that exaggerated VGCC functionality from 2D cultured SCG cells is possibly due to differences in membrane architecture, characterized by uniquely organized caveolar lipid rafts. The practical implication of use of 3D-cultured cells in preclinical drug discovery studies is that such platforms would be more effective in eliminating false positive hits and as such improve the overall yield from screening campaigns.

  10. Failure of intravenous lipid emulsion in treatment of cardiotoxicity caused by mixed overdose including dihydropyridine calcium channel blockers

    Directory of Open Access Journals (Sweden)

    Jović-Stošić Jasmina

    2016-01-01

    Full Text Available Introduction. Calcium channel blockers and beta-blockers are among the most frequently ingested cardiovascular drugs in self-poisoning causing significant mortality. Intravenous lipid emulsion (ILE is reported as a potentially novel antidote for treatment of acute poisoning caused by some of these drugs. Case report. We presented two cases of poisoning with these drugs. The case 1, a 24-year-old woman ingested amplodipine, metformin and gliclazide for self-poisoning. She presented with tachycardia and hypotension. Laboratory analyses revealed hyperglycaemia and metabolic acidosis. Despite the treatment which included fluid resuscitation, vasopressors, intravenous calcium, glucagon and ILE, circulatory shock occurred. The patient died 10 hours after admission due to cardiac arrest refractory to cardiopulmonary resuscitation. The case 2, a 41-year old man, was found in a coma with empty packages of nifedipine, metoprolol and diazepam tablets. On admission vital signs included Glasgow Coma Scale (GCS of 3, weak palpable pulses, undetectable blood pressure, and irregular breathing with oxygen saturation of 60%. An electrocardiography showed AV block (Mobitz II with ventricular rate of 44/min with progression to third degree of AV block. In attempt to increase heart rate and blood pressure the following agents were administered: atropine boluses, normal saline with dopamine, glucagon, calcium chloride and ILE. Temporary transvenous pacemaker was placed, electrical capture was recorded, but without improvement in haemodynamics. Three hours after admission cardiac arrest happened and cardiopulmonary resuscitation was unsuccessful. Conclusion. Intravenous lipid emulsion may be ineffective in acute poisonings with amlodipine, nifedipine or metoprolol.

  11. Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate.

    Science.gov (United States)

    Ivanov, Vadim; Ivanova, Svetlana; Kalinovsky, Tatiana; Niedzwiecki, Aleksandra; Rath, Matthias

    2016-01-01

    Calcium, sodium and potassium channel blockers are widely prescribed medications for a variety of health problems, most frequently for cardiac arrhythmias, hypertension, angina pectoris and other disorders. However, chronic application of channel blockers is associated with numerous side effects, including worsening cardiac pathology. For example, nifedipine, a calcium-channel blocker was found to be associated with increased mortality and increased risk for myocardial infarction. In addition to the side effects mentioned above by different channel blockers, these drugs can cause arterial wall damage, thereby contributing to vascular wall structure destabilization and promoting events facilitating rupture of plaques. Collagen synthesis is regulated by ascorbic acid, which is also essential for its optimum structure as a cofactor in lysine and proline hydroxylation, a precondition for optimum crosslinking of collagen and elastin. Therefore, the main objective in this study was to evaluate effects of various types of channel blockers on intracellular accumulation and cellular functions of ascorbate, specifically in relation to formation and extracellular deposition of major collagen types relevant for vascular function. Effects of select Na- and Ca- channel blockers on collagen synthesis and deposition were evaluated in cultured human dermal fibroblasts and aortic smooth muscle cells by immunoassay. All channel blockers tested demonstrated inhibitory effects on collagen type I deposition to the ECM by fibroblasts, each to a different degree. Ascorbic acid significantly increased collagen I ECM deposition. Nifedipine (50 µM), a representative of channel blockers tested, significantly reduced ascorbic acid and ascorbyl palmitate-dependent ECM deposition of collagen type l and collagen type lV by cultured aortic smooth muscle cells. In addition, nifedipine (50 µM) significantly reduced ascorbate-dependent collagen type l and type lV synthesis by cultured aortic smooth

  12. Hyperpolarization-activated cation and T-type calcium ion channel expression in porcine and human renal pacemaker tissues.

    Science.gov (United States)

    Hurtado, Romulo; Smith, Carl S

    2016-05-01

    Renal pacemaker activity triggers peristaltic upper urinary tract contractions that propel waste from the kidney to the bladder, a process prone to congenital defects that are the leading cause of pediatric kidney failure. Recently, studies have discovered that hyperpolarization-activated cation (HCN) and T-type calcium (TTC) channel conductances underlie murine renal pacemaker activity, setting the origin and frequency and coordinating upper urinary tract peristalsis. Here, we determined whether this ion channel expression is conserved in the porcine and human urinary tracts, which share a distinct multicalyceal anatomy with multiple pacemaker sites. Double chromagenic immunohistochemistry revealed that HCN isoform 3 is highly expressed at the porcine minor calyces, the renal pacemaker tissues, whereas the kidney and urinary tract smooth muscle lacked this HCN expression. Immunofluorescent staining demonstrated that HCN(+) cells are integrated within the porcine calyx smooth muscle, and that they co-express TTC channel isoform Cav3.2. In humans, the anatomic structure of the minor calyx pacemaker was assayed via hematoxylin and eosin analyses, and enabled the visualization of the calyx smooth muscle surrounding adjacent papillae. Strikingly, immunofluorescence revealed that HCN3(+) /Cav3.2(+) cells are also localized to the human minor calyx smooth muscle. Collectively, these data have elucidated a conserved molecular signature of HCN and TTC channel expression in porcine and human calyx pacemaker tissues. These findings provide evidence for the mechanisms that can drive renal pacemaker activity in the multi-calyceal urinary tract, and potential causes of obstructive uropathies. PMID:26805464

  13. Effects of low-level laser exposure on calcium channels and intracellular release in cultured astrocytes

    Science.gov (United States)

    Mang, Thomas S.; Maneshi, Mohammed M.; Shucard, David W.; Hua, Susan; Sachs, Frederick

    2016-03-01

    Prompted by a study of traumatic brain injury (TBI) in a model system of cultured astrocytes, we discovered that low level laser illumination (LLL) at 660nm elevates the level of intracellular Ca2+. The coherence of the illumination was not essential since incoherent red light also worked. For cells bathed in low Ca2+ saline so that influx was suppressed, the Ca2+ level rose with no significant latency following illumination and consistent with a slow leak of Ca2+ from storage such as from the endoplasmic reticulum and/or mitochondria. When the cells were bathed in normal Ca2+ saline, the internal Ca2+ rose, but with a latency of about 17 seconds from the beginning of illumination. Pharmacologic studies with ryanodine inhibited the light effect. Testing the cells with fluid shear stress as used in the TBI model showed that mechanically induced elevation of cell Ca2+ was unaffected by illumination.

  14. A Putative Calcium-Permeable Cyclic Nucleotide-Gated Channel, CNGC18, Regulates Polarized Pollen Tube Growth

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A tip-focused Ca2+ gradient is tightly coupled to polarized pollen tube growth, and tip-localized influxes of extracellular Ca2+ are required for this process. However the molecular identity and regulation of the potential Ca2+ channels remains elusive.The present study has implicated CNGC18 (cyclic nucleotide-gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca2+]ex). CNGC18-yellow fluorescence protein (YFP)was preferentially localized to the apparent post-Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes.The PM localization was affected by tip-localized ROP1 signaling. Expression of wild type ROP1 or an active form of ROP1enhanced CNGC18-YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator)blocked the PM localization. These results support a role for PM-localized CNGC18 in the regulation of polarized pollen tube growth through Its potential function in the modulation of calcium influxes.

  15. Calcium-mediated agonists activate an inwardly rectified K+ channel in colonic secretory cells.

    Science.gov (United States)

    Devor, D C; Frizzell, R A

    1993-11-01

    Single-channel recording techniques were used to identify and characterize the K+ channel activated by Ca(2+)-mediated secretory agonists in T84 cells. Carbachol (CCh; 100 microM) and taurodeoxycholate (TDC; 0.75 mM) stimulated oscillatory outward K+ currents. With K gluconate in bath and pipette, cell-attached single-channel K+ currents stimulated by CCh and ionomycin (2 microM) were inwardly rectified and reversed at 0 mV. The single-channel chord conductance was 32 pS at -90 mV and 14 pS at +90 mV. Similar properties were observed in excised inside-out patches in symmetric K+, permitting further characterization of channel properties. Partial substitution of bath or pipette K+ with Na+ gave a K(+)-to-Na+ selectivity ratio of 5.5:1. Channel activity increased with increasing bath Ca2+ concentration in the physiological range of 50-800 nM. Maximal channel activity occurred at intracellular pH 7.2 and decreased at more acidic or alkaline pH values. Extracellular charybdotoxin (CTX; 50 nM) blocked inward but not outward currents. Extracellular tetraethylammonium (TEA; 10 mM) reduced single-channel amplitude at all voltages. No apparent block of the channel was observed with extracellular Ba2+ (1 mM), apamin (1 microM), 4-aminopyridine (4-AP; 4 mM), quinine (500 microM), or glyburide (10 microM). Cytosolic quinine and 4-AP blocked both inward and outward currents, whereas Ba2+ blocked only outward currents. Apamin, CTX, TEA, and glyburide did not affect channel activity. The agonist activation and pharmacological profile of this inwardly rectified K+ channel indicate that it is responsible for the increase in basolateral K+ conductance stimulated by Ca(2+)-mediated agonists in T84 cells. PMID:7694492

  16. Splice variants of the CaV1.3 L-type calcium channel regulate dendritic spine morphology

    Science.gov (United States)

    Stanika, Ruslan; Campiglio, Marta; Pinggera, Alexandra; Lee, Amy; Striessnig, Jörg; Flucher, Bernhard E.; Obermair, Gerald J.

    2016-01-01

    Dendritic spines are the postsynaptic compartments of glutamatergic synapses in the brain. Their number and shape are subject to change in synaptic plasticity and neurological disorders including autism spectrum disorders and Parkinson’s disease. The L-type calcium channel CaV1.3 constitutes an important calcium entry pathway implicated in the regulation of spine morphology. Here we investigated the importance of full-length CaV1.3L and two C-terminally truncated splice variants (CaV1.342A and CaV1.343S) and their modulation by densin-180 and shank1b for the morphology of dendritic spines of cultured hippocampal neurons. Live-cell immunofluorescence and super-resolution microscopy of epitope-tagged CaV1.3L revealed its localization at the base-, neck-, and head-region of dendritic spines. Expression of the short splice variants or deletion of the C-terminal PDZ-binding motif in CaV1.3L induced aberrant dendritic spine elongation. Similar morphological alterations were induced by co-expression of densin-180 or shank1b with CaV1.3L and correlated with increased CaV1.3 currents and dendritic calcium signals in transfected neurons. Together, our findings suggest a key role of CaV1.3 in regulating dendritic spine structure. Under physiological conditions it may contribute to the structural plasticity of glutamatergic synapses. Conversely, altered regulation of CaV1.3 channels may provide an important mechanism in the development of postsynaptic aberrations associated with neurodegenerative disorders. PMID:27708393

  17. Current concepts in combination therapy for the treatment of hypertension: combined calcium channel blockers and RAAS inhibitors

    Directory of Open Access Journals (Sweden)

    Alberto F Rubio-Guerra

    2009-11-01

    Full Text Available Alberto F Rubio-Guerra1, David Castro-Serna2, Cesar I Elizalde Barrera2, Luz M Ramos-Brizuela21Metabolic and Research Clinic, 2Internal Medicine Department, Hospital General de Ticomán SS DF, MéxicoAbstract: Recent guidelines for the management of hypertension recommend target blood pressures <140/90 mmHg in hypertensive patients, or <130/80 mmHg in subjects with diabetes, chronic kidney disease, or coronary artery disease. Despite the availability and efficacy of antihypertensive drugs, most hypertensive patients do not reach the recommended treatment targets with monotherapy, making combination therapy necessary to achieve the therapeutic goal. Combination therapy with 2 or more agents is the most effective method for achieving strict blood pressure goals. Fixed-dose combination simplifies treatment, reduces costs, and improves adherence. There are many drug choices for combination therapy, but few data are available about the efficacy and safety of some specific combinations. Combination therapy of calcium antagonists and inhibitors of the renin-angiotensin-aldosterone system (RAAS are efficacious and safe, and have been considered rational by both the JNC 7 and the 2007 European Society of Hypertension – European Society of Cardiology guidelines for the management of arterial hypertension. The aim of this review is to discuss some relevant issues about the use of combinations with calcium channel blockers and RAAS inhibitors in the treatment of hypertension.Keywords: hypertension, calcium channel blockers, renin-angiotensin-aldosterone system inhibitors, fixed-dose combination, adherence

  18. Anion channels in Chara corallina tonoplast membrane: Calcium dependence and rectification

    NARCIS (Netherlands)

    Berecki, G.; Varga, Z.; Iren, F. van; Duijn, B. van

    1999-01-01

    Tonoplast K+ channels of Chara corallina are well characterized but only a few reports mention anion channels, which are likely to play an important role in the tonoplast action potential and osmoregulation of this plant. For experiments internodal cells were isolated. Cytoplasmic droplets were form

  19. Current insights into the physiology of the epithelial calcium and magnesium channels

    NARCIS (Netherlands)

    Topala, C.N.

    2008-01-01

    Ion channels are specialized proteins that span the plasma membrane of living cells allowing ion fluxes through this essentially impermeable barrier. Most ion channels show selectivity in that their pores are more permeable to some ions than to others. The development of the patch-clamp technique en

  20. Role of calcium activated potassium channels in atrial fibrillation pathophysiology and therapy

    DEFF Research Database (Denmark)

    Diness, Jonas G.; Bentzen, Bo H.; S. Sørensen, Ulrik;

    2015-01-01

    Small-conductance Ca2+-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels since they might constitute a relatively atrial selective target. The present review will give...

  1. The Epithelial Calcium Channel TRPV5 Is Regulated Differentially by Klotho and Sialidase.

    NARCIS (Netherlands)

    Leunissen, E.H.P.; Nair, A.V.; Büll, C.; Lefeber, D.J.; Delft, F.L. van; Bindels, R.J.M.; Hoenderop, J.G.J.

    2013-01-01

    The transient receptor potential vanilloid type 5 (TRPV5) Ca(2+) channel facilitates transcellular Ca(2+) transport in the distal convoluted tubule (DCT) of the kidney. The channel is glycosylated with a complex type N-glycan and it has been postulated that hydrolysis of the terminal sialic acid(s)

  2. Calcium-activated potassium channels - a therapeutic target for modulating nitric oxide in cardiovascular disease?

    DEFF Research Database (Denmark)

    Dalsgaard, Thomas; Kroigaard, Christel; Simonsen, Ulf

    2010-01-01

    : Opening of SK and IK channels is associated with EDHF-type vasodilatation, but, through increased endothelial cell Ca(2+) influx, L-arginine uptake, and decreased ROS production, it may also lead to increased NO bioavailability and endothelium-dependent vasodilatation. TAKE HOME MESSAGE: Opening of SK and...... IK channels can increase both EDHF and NO-mediated vasodilatation. Therefore, openers of SK and IK channels may have the potential of improving endothelial cell function in cardiovascular disease.......-dependent vasodilatation is mediated by NO, prostacyclin, and an endothelium-derived hyperpolarising factor (EDHF), and involves small (SK) and intermediate (IK) conductance Ca(2+)-activated K(+) channels. Therefore, SK and IK channels may be drug targets for the treatment of endothelial dysfunction in cardiovascular...

  3. Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

    Energy Technology Data Exchange (ETDEWEB)

    Ostrow, Lyle W., E-mail: lostrow1@jhmi.edu [Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD 21205 (United States); Suchyna, Thomas M.; Sachs, Frederick [Department of Physiology and Biophysical Sciences, State University of New York at Buffalo, Buffalo, NY 14214 (United States)

    2011-06-24

    Highlights: {yields} Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. {yields} Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca{sup 2+} permeant SACs. {yields} The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. {yields} Stretch-induced ET-1 production depends on a calcium influx. {yields} SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (<20%) of a rubber substrate increased ET-1 secretion, and 4 {mu}M GsMTx-4 (a specific inhibitor of SACs) inhibited secretion by 30%. GsMTx-4 did not alter basal ET-1 levels in the absence of stretch. Decreasing the calcium influx by lowering extracellular calcium also inhibited stretch-induced ET-1 secretion without effecting ET-1 secretion in unstretched controls. Furthermore, inhibiting SACs with the less specific inhibitor streptomycin also inhibited stretch-induced ET-1 secretion. The data can be explained with a simple model in which ET-1 secretion depends on an internal Ca{sup 2+} threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.

  4. An evaluation of vardenafil as a calcium channel blocker in pulmonary artery in rats

    Directory of Open Access Journals (Sweden)

    Edibe Minareci

    2014-01-01

    Full Text Available Objective: Vardenafil was reported to relax rat pulmonary artery through endothelium-dependent mechanisms. The aim of this in vitro study was to investigate other related mechanisms for this effect. Materials and Methods: Endothelium-intact and denuded artery rings were suspended in order to record isometric tension. In the rings with or without endothelium, the concentration-response curves for vardenafil were generated. In the rings without endothelium the contractile response induced by phenylephrine (Phe or KCl was assessed in the presence or absence of vardenafil. In the last set of experiments, pulmonary artery rings were exposed to calcium-free isotonic depolarizing solution and the contractile response induced by the addition of calcium was evaluated in the presence or absence of vardenafil, nifedipine, verapamil or 1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one (ODQ. Results: Vardenafil attenuated pulmonary artery contraction induced by phenylephrine in the presence and absence of endothelium. In addition, vardenafil attenuated both Phe or KCl-induced contraction but, it′s effect on the KCl dose-response curve was more significant. Vardenafil also inhibited the contractile response induced by calcium in a dose-dependent manner. Addition of nifedipine or verapamil did not significantly alter this effect while ODQ incubation significantly inhibited vardenafil-induced relaxation. Conclusion: From these findings, it was proposed that vardenafil relaxed rat pulmonary artery through inhibiting calcium influx.

  5. Complex actions of ionomycin in cultured cerebellar astrocytes affecting both calcium-induced calcium release and store-operated calcium entry

    DEFF Research Database (Denmark)

    Müller, Margit S; Obel, Linea Lykke Frimodt; Waagepetersen, Helle S;

    2013-01-01

    The polyether antibiotic ionomycin is a common research tool employed to raise cytosolic Ca(2+) in almost any cell type. Although initially thought to directly cause physicochemical translocation of extracellular Ca(2+) into the cytosol, a number of studies have demonstrated that the mechanism of......(2+), consisting of an initial peak and a subsequent sustained plateau. The response was dependent on concentration and exposure time. While the plateau phase was abolished in the absence of extracellular Ca(2+), the peak phase persisted. The peak amplitude could be lowered significantly...... by application of dantrolene, demonstrating involvement of Ca(2+)-induced Ca(2+)-release (CICR). The plateau phase was markedly reduced when store-operated Ca(2+)-entry (SOCE) was blocked with 2-aminoethoxydiphenyl borate. Our results show that ionomycin directly affects internal Ca(2+) stores in astrocytes...

  6. Co-localization of putative calcium channels (phenylalkylamine-binding sites) on oil bodies in protoplasts from dark-grown sunflower seedling cotyledons.

    Science.gov (United States)

    Vandana, Shweta; Bhatla, Satish C

    2009-07-01

    Oil bodies are spherical entities containing a triacylglycerol (TAG) matrix encased by a phospholipid monolayer, which is stabilized by oil body-specific proteins, principally oleosins. Biochemical investigations in the recent past have also demonstrated the expression of calcium-binding proteins, called caleosins, as a component of oil body membranes during seed germination. Using DM-Bodipy-phenylalkylamine (PAA; a fluorescent derivative of phenylalkylamine)-a fluorescent probe known to bind L-type calcium channel proteins, present investigations provide the first report on the localization and preferential accumulation of putative calcium channel proteins on/around oil bodies during peak lipolytic phase in protoplasts derived from dark-grown sunflower (Helianthus annuus L. cv Morden) seedling cotyledons. Specificity of DM-Bodipy-PAA labeling was confirmed by using bepridil, a non-fluorescent competitor of PAA while non-specific dye accumulation has been ruled out by using Bodipy-FL as control. Co-localization of fluorescence from DM-Bodipy-PAA binding sites (ex: 504 nm; em: 511 nm) and nile red fluorescing oil bodies (ex: 552 nm; em: 636 nm) has been undertaken by epifluorescence and confocal laser scanning microscopy (CLSM). It revealed the affinity of PAA-sensitive ion channels for the oil body surface. Findings from the current investigations highlight the significance of calcium and calcium channel proteins during oil body mobilization in sunflower.

  7. External bioenergy-induced increases in intracellular free calcium concentrations are mediated by Na+/Ca2+ exchanger and L-type calcium channel.

    Science.gov (United States)

    Kiang, Juliann G; Ives, John A; Jonas, Wayne B

    2005-03-01

    External bioenergy (EBE, energy emitted from a human body) has been shown to increase intracellular calcium concentration ([Ca2+]i, an important factor in signal transduction) and regulate the cellular response to heat stress in cultured human lymphoid Jurkat T cells. In this study, we wanted to elucidate the underlying mechanisms. A bioenergy specialist emitted bioenergy sequentially toward tubes of cultured Jurkat T cells for one 15-minute period in buffers containing different ion compositions or different concentrations of inhibitors. [Ca2+], was measured spectrofluorometrically using the fluorescent probe fura-2. The resting [Ca2+]i in Jurkat T cells was 70 +/- 3 nM (n = 130) in the normal buffer. Removal of external calcium decreased the resting [Ca2+]i to 52 +/- 2 nM (n = 23), indicating that Ca2+ entry from the external source is important for maintaining the basal level of [Ca2+]i. Treatment of Jurkat T cells with EBE for 15 min increased [Ca2+]i by 30 +/- 5% (P EBE did not attenuate [Ca2+]i responsiveness to EBE. Removal of external Ca2+ or Na+, but not Mg2+, inhibited the EBE-induced increase in [Ca2+]i. Dichlorobenzamil, an inhibitor of Na+/Ca2+ exchangers, also inhibited the EBE-induced increase in [Ca2+]i in a concentration-dependent manner with an IC50 of 0.11 +/- 0.02 nM. When external [K+] was increased from 4.5 mM to 25 mM, EBE decreased [Ca2+]i. The EBE-induced increase was also blocked by verapamil, an L-type voltage-gated Ca2+ channel blocker. These results suggest that the EBE-induced [Ca2+]i increase may serve as an objective means for assessing and validating bioenergy effects and those specialists claiming bioenergy capability. The increase in [Ca2+]i is mediated by activation of Na+/Ca2+ exchangers and opening of L-type voltage-gated Ca2+ channels.

  8. Membrane sialic acid influences basophil histamine release by interfering with calcium dependence

    DEFF Research Database (Denmark)

    Jensen, C; Norn, S; Skov, P S;

    1987-01-01

    The influence of the cell membrane content of sialic acid on basophil histamine release was examined in vitro in allergic patients and normal controls. Enzymatical removal of sialic acid enhanced histamine release induced by allergen and anti-IgE, whereas an increase in membrane sialic acid content...

  9. Effects of exogenous hydrogen sulphide on calcium signalling, background (TASK) K channel activity and mitochondrial function in chemoreceptor cells.

    Science.gov (United States)

    Buckler, Keith J

    2012-04-01

    It has been proposed that endogenous H(2)S mediates oxygen sensing in chemoreceptors; this study investigates the mechanisms by which H(2)S excites carotid body type 1 cells. H(2)S caused a rapid reversible increase in intracellular calcium with EC(50) ≈ 6 μM. This [Ca(2+)](i) response was abolished in Ca-free Tyrode. In perforated patch current clamp recordings, H(2)S depolarised type 1 cells from -59 to -35 mV; this was accompanied by a robust increase in [Ca(2+)](i). Voltage clamping at the resting membrane potential abolished the H(2)S-induced rise in [Ca(2+)](i). H(2)S inhibited background K(+) current in whole cell perforated patch and reduced background K(+) channel activity in cell-attached patch recordings. It is concluded that H(2)S excites type 1 cells through the inhibition of background (TASK) potassium channels leading to membrane depolarisation and voltage-gated Ca(2+) entry. These effects mimic those of hypoxia. H(2)S also inhibited mitochondrial function over a similar concentration range as assessed by NADH autofluorescence and measurement of intracellular magnesium (an index of decline in MgATP). Cyanide inhibited background K channels to a similar extent to H(2)S and prevented H(2)S exerting any further influence over channel activity. These data indicate that the effects of H(2)S on background K channels are a consequence of inhibition of oxidative phosphorylation. Whilst this does not preclude a role for endogenous H(2)S in oxygen sensing via the inhibition of cytochrome oxidase, the levels of H(2)S required raise questions as to the viability of such a mechanism.

  10. A toxic extract of the marine phytoflagellate Prymnesium parvum induces calcium-dependent release of glutamate from rat brain synaptosomes.

    Science.gov (United States)

    Mariussen, Espen; Nelson, George Nicholas; Fonnum, Frode

    2005-01-01

    Blooms of the marine phytoflagellate Prymnesium parvum produced mass mortality of fish in Norway and many other parts of the world. The effects of a purified algae extract of P. parvum on transmitter release from rat brain synaptosomes were studied to characterize its toxic action. Synaptosomes are detached nerve terminals and represent a simple system that has retained the machinery for uptake, synthesis, storage, and release of neurotransmitters. A crude methanol extract of P. parvum was purified by reverse-phase column for fast protein liquid chromatography (FPLC). The purified extract stimulated Ca2+-dependent spontaneous release of glutamate in a concentration-dependent manner. The release was increased by addition of extracellular Ca2+. The release of glutamate was suppressed by the Ca2+-channel blockers flunarizine (10 microM), diltiazem (10 microM), and verapamil (10 microM). The stimulation of release of glutamate from rat brain synaptosomes induced by the toxin may be due to an ionophorelike property of the algae extract such as previously reported for the potent algal toxin maitotoxin. At high concentrations the toxin primarily acts as a powerful lytic agent. PMID:15739805

  11. Effects of extracellular calcium concentration on the glutamate release by bioactive glass (BG60S) preincubated osteoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Valerio, P; Leite, M Fatima [Department of Physiology and Biophysics, Federal University of Minas Gerais (Brazil); Pereira, M M [Department of Metallurgical Engineering, Federal University of Minas Gerais (Brazil); Goes, A M, E-mail: patricia.valerio@terra.com.b, E-mail: leitemd@dedalus.lcc.ufmg.b, E-mail: mpereira@demet.ufmg.b, E-mail: goes@icb.ufmg.b [Department of Biochemistry and Immunology, Federal University of Minas Gerais (Brazil)

    2009-08-15

    Glutamate released by osteoblasts sharing similarities with its role in neuronal transmission is a very new scientific concept which actually changed the understanding of bone physiology. Since glutamate release is a calcium (Ca{sup 2+})-dependent process and considering that we have previously demonstrated that the dissolution of bioactive glass with 60% of silicon (BG60S) can alter osteoblast Ca{sup 2+}-signaling machinery, we investigated whether BG60S induces glutamate secretion in osteoblasts and whether it requires an increase in intracellular Ca{sup 2+}. Here we showed that the extracellular Ca{sup 2+} increase due to BG60S dissolution leads to an intracellular Ca{sup 2+} increase in the osteoblast, through the activation of an inositol 1,4,5-triphosphate receptor (InsP{sub 3}R) and a ryanodine receptor (RyR). Additionally, we also demonstrated that glutamate released by osteoblasts can be profoundly altered by BG60S. The modulation of osteoblast glutamate released by the extracellular Ca{sup 2+} concentration opens a new window in the field of tissue engineering, since many biomaterials used for bone repair are able to increase the extracellular Ca{sup 2+} concentration due to their dissolution products.

  12. TRPV channel-mediated calcium transients in nociceptor neurons are dispensable for avoidance behaviour

    OpenAIRE

    Lindy, Amanda S.; Parekh, Puja K.; Zhu, Richard; Kanju, Patrick; Chintapalli, Sree V.; Tsvilovskyy, Volodymyr; Patterson, Randen L.; Anishkin, Andriy; van Rossum, Damian B.; Liedtke, Wolfgang B.

    2014-01-01

    Animals need to sense and react to potentially dangerous environments. TRP ion channels participate in nociception, presumably via Ca2+ influx, in most animal species. However, the relationship between ion permeation and animals’ nocifensive behaviour is unknown. Here we use an invertebrate animal model with relevance for mammalian pain. We analyse the putative selectivity filter of OSM-9, a TRPV channel, in osmotic avoidance behaviour of Caenorhabditis elegans. Using mutagenized OSM-9 expres...

  13. Analgesic effects of a substituted N-triazole oxindole (TROX-1), a state-dependent, voltage-gated calcium channel 2 blocker.

    Science.gov (United States)

    Abbadie, Catherine; McManus, Owen B; Sun, Shu-Yu; Bugianesi, Randal M; Dai, Ge; Haedo, Rodolfo J; Herrington, James B; Kaczorowski, Gregory J; Smith, McHardy M; Swensen, Andrew M; Warren, Vivien A; Williams, Brande; Arneric, Stephen P; Eduljee, Cyrus; Snutch, Terrance P; Tringham, Elizabeth W; Jochnowitz, Nina; Liang, Annie; Euan MacIntyre, D; McGowan, Erin; Mistry, Shruti; White, Valerie V; Hoyt, Scott B; London, Clare; Lyons, Kathryn A; Bunting, Patricia B; Volksdorf, Sylvia; Duffy, Joseph L

    2010-08-01

    Voltage-gated calcium channel (Ca(v))2.2 (N-type calcium channels) are key components in nociceptive transmission pathways. Ziconotide, a state-independent peptide inhibitor of Ca(v)2.2 channels, is efficacious in treating refractory pain but exhibits a narrow therapeutic window and must be administered intrathecally. We have discovered an N-triazole oxindole, (3R)-5-(3-chloro-4-fluorophenyl)-3-methyl-3-(pyrimidin-5-ylmethyl)-1-(1H-1,2,4-triazol-3-yl)-1,3-dihydro-2H-indol-2-one (TROX-1), as a small-molecule, state-dependent blocker of Ca(v)2 channels, and we investigated the therapeutic advantages of this compound for analgesia. TROX-1 preferentially inhibited potassium-triggered calcium influx through recombinant Ca(v)2.2 channels under depolarized conditions (IC(50) = 0.27 microM) compared with hyperpolarized conditions (IC(50) > 20 microM). In rat dorsal root ganglion (DRG) neurons, TROX-1 inhibited omega-conotoxin GVIA-sensitive calcium currents (Ca(v)2.2 channel currents), with greater potency under depolarized conditions (IC(50) = 0.4 microM) than under hyperpolarized conditions (IC(50) = 2.6 microM), indicating state-dependent Ca(v)2.2 channel block of native as well as recombinant channels. TROX-1 fully blocked calcium influx mediated by a mixture of Ca(v)2 channels in calcium imaging experiments in rat DRG neurons, indicating additional block of all Ca(v)2 family channels. TROX-1 reversed inflammatory-induced hyperalgesia with maximal effects equivalent to nonsteroidal anti-inflammatory drugs, and it reversed nerve injury-induced allodynia to the same extent as pregabalin and duloxetine. In contrast, no significant reversal of hyperalgesia was observed in Ca(v)2.2 gene-deleted mice. Mild impairment of motor function in the Rotarod test and cardiovascular functions were observed at 20- to 40-fold higher plasma concentrations than required for analgesic activities. TROX-1 demonstrates that an orally available state-dependent Ca(v)2 channel blocker may

  14. Cav1.4 L-Type Calcium Channels Contribute to Calpain Activation in Degenerating Photoreceptors of rd1 Mice.

    Directory of Open Access Journals (Sweden)

    Christian Schön

    Full Text Available Retinitis pigmentosa is an inherited blinding disorder characterized by progressive degeneration and loss of photoreceptors. The exact mechanism of degeneration and cell death of photoreceptors is not known, but is thought to involve disturbed Ca2+-signaling. Ca2+ can enter the photoreceptor cell via outer segment cyclic nucleotide-gated (CNG channels or synaptic Cav1.4 L-type voltage-gated calcium channels (VGCC. Previously, we have shown that genetic ablation of the Cngb1 gene encoding the B subunit of the rod CNG channel delays the fast progressing degeneration in the rd1 mutant mouse model of retinitis pigmentosa. In this study, we crossbred rd1 mice with the Cacna1f-deficient mouse lacking the Cav1.4 α1 subunit of the L-type VGCC. Longitudinal in vivo examinations of photoreceptor layer thickness by optical coherence tomography revealed a significant, but not sustained delay of retinal degeneration in Cacna1f x rd1 double mutant mice compared to rd1 mice. This was accompanied by a reduction of TUNEL positive cells in the early phase of rod degeneration. Remarkably, Cacna1f x rd1 double mutant mice displayed a strong decrease in the activation of the Ca2+-dependent protease calpain during photoreceptor loss. Our results show that genetic deletion of the synaptic Cav1.4 L-type VGCCs impairs calpain activation and leads to a short-term preservation of photoreceptors in the rd1 mouse.

  15. Inhibition of T-Type Voltage Sensitive Calcium Channel Reduces Load-Induced OA in Mice and Suppresses the Catabolic Effect of Bone Mechanical Stress on Chondrocytes.

    Directory of Open Access Journals (Sweden)

    Padma P Srinivasan

    Full Text Available Voltage-sensitive calcium channels (VSCC regulate cellular calcium influx, one of the earliest responses to mechanical stimulation in osteoblasts. Here, we postulate that T-type VSCCs play an essential role in bone mechanical response to load and participate in events leading to the pathology of load-induced OA. Repetitive mechanical insult was used to induce OA in Cav3.2 T-VSCC null and wild-type control mouse knees. Osteoblasts (MC3T3-E1 and chondrocytes were treated with a selective T-VSCC inhibitor and subjected to fluid shear stress to determine how blocking of T-VSCCs alters the expression profile of each cell type upon mechanical stimulation. Conditioned-media (CM obtained from static and sheared MC3T3-E1 was used to assess the effect of osteoblast-derived factors on the chondrocyte phenotype. T-VSCC null knees exhibited significantly lower focal articular cartilage damage than age-matched controls. In vitro inhibition of T-VSCC significantly reduced the expression of both early and late mechanoresponsive genes in osteoblasts but had no effect on gene expression in chondrocytes. Furthermore, treatment of chondrocytes with CM obtained from sheared osteoblasts induced expression of markers of hypertrophy in chondrocytes and this was nearly abolished when osteoblasts were pre-treated with the T-VSCC-specific inhibitor. These results indicate that T-VSCC plays a role in signaling events associated with induction of OA and is essential to the release of osteoblast-derived factors that promote an early OA phenotype in chondrocytes. Further, these findings suggest that local inhibition of T-VSCC may serve as a therapy for blocking load-induced bone formation that results in cartilage degeneration.

  16. Action potential-evoked calcium release is impaired in single skeletal muscle fibers from heart failure patients.

    Directory of Open Access Journals (Sweden)

    Marino DiFranco

    Full Text Available BACKGROUND: Exercise intolerance in chronic heart failure (HF has been attributed to abnormalities of the skeletal muscles. Muscle function depends on intact excitation-contraction coupling (ECC, but ECC studies in HF models have been inconclusive, due to deficiencies in the animal models and tools used to measure calcium (Ca2+ release, mandating investigations in skeletal muscle from HF patients. The purpose of this study was to test the hypothesis that Ca2+ release is significantly impaired in the skeletal muscle of HF patients in whom exercise capacity is severely diminished compared to age-matched healthy volunteers. METHODS AND FINDINGS: Using state-of-the-art electrophysiological and optical techniques in single muscle fibers from biopsies of the locomotive vastus lateralis muscle, we measured the action potential (AP-evoked Ca2+ release in 4 HF patients and 4 age-matched healthy controls. The mean peak Ca2+ release flux in fibers obtained from HF patients (10±1.2 µM/ms was markedly (2.6-fold and significantly (p<0.05 smaller than in fibers from healthy volunteers (28±3.3 µM/ms. This impairment in AP-evoked Ca2+ release was ubiquitous and was not explained by differences in the excitability mechanisms since single APs were indistinguishable between HF patients and healthy volunteers. CONCLUSIONS: These findings prove the feasibility of performing electrophysiological experiments in single fibers from human skeletal muscle, and offer a new approach for investigations of myopathies due to HF and other diseases. Importantly, we have demonstrated that one step in the ECC process, AP-evoked Ca2+ release, is impaired in single muscle fibers in HF patients.

  17. Assessment of the role of NMDA receptors and calcium channels in glucocorticoid-induced enhancement of memory consolidation in mice

    Directory of Open Access Journals (Sweden)

    Vafaei AA

    2009-10-01

    Full Text Available "n Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;} Background: Ample evidence indicated that glucocorticoids, when administered after training, enhance memory consolidation in a variety of tasks. The mechanisms underlying the enhancing effects of glucocorticoids on memory consolidation are not well known. The aim of this study was to determine the role of NMDA receptors and calcium channels in glucocorticoid-induced enhancement of avoidance memory consolidation in mice."n"nMethods: Experiments were performed on 166 male albino mice (about 30gr. The animals were trained in an inhibitory avoidance (IA task (0.5mA shock for 3 seconds. In Experiment 1, dose- response effects of corticosterone on memory consolidation were determined. Immediately after training in IA task, the animals were received different doses of corticosterone (0.3, 1 or 3mg/kg. In Experiments 2 and 3, effects of corticosterone on memory consolidation were examined in the presence or absence of verapamil, a calcium channel blocker, (2.5, 5 or 20mg/kg or MK-801, an antagonist of NMDA receptor (0.1mg/kg, respectively. In all experiments, retention test was done two days later."n"nResults: Results from first experiment revealed that corticosterone at dose of 0.3mg/kg significantly improved consolidation of

  18. Ethanol's effects on neurotransmitter release and intracellular free calcium in PC12 cells

    International Nuclear Information System (INIS)

    The effect of ethanol on muscarine-stimulated release of [3H]NE was studied using the rat pheochromocytoma cell line, PC12. At concentrations of 25 mM and above, ethanol produced a dose dependent inhibition of muscarine-stimulated release of [3H]NE. The inhibition of muscarine-stimulated transmitter release occurred in the absence of any effect of ethanol on [3H]NE uptake, metabolism or on muscarinic binding to the cells. However, ethanol produced an inhibition of muscarine-stimulated elevation of intracellular free Ca2+ which corresponded with the inhibition of transmitter release. At concentrations greater than 100 mM, ethanol produced both a stimulation of the release of [3H]NE as well as an increase in intracellular free Ca2+. The increase in basal transmitter release and intracellular free Ca2+ occurred independent of the inhibition by ethanol of muscarine-stimulated elevation of intracellular free Ca2+ or transmitter section. These results demonstrate the relationship of the effects of ethanol on cellular free Ca2+ and neurotransmitter release

  19. Autosomal dominant hypercalciuria in a mouse model due to a mutation of the epithelial calcium channel, TRPV5.

    Directory of Open Access Journals (Sweden)

    Nellie Y Loh

    Full Text Available Hypercalciuria is a major cause of nephrolithiasis, and is a common and complex disorder involving genetic and environmental factors. Identification of genetic factors for monogenic forms of hypercalciuria is hampered by the limited availability of large families, and to facilitate such studies, we screened for hypercalciuria in mice from an N-ethyl-N-nitrosourea mutagenesis programme. We identified a mouse with autosomal dominant hypercalciuria (HCALC1. Linkage studies mapped the Hcalc1 locus to a 11.94 Mb region on chromosome 6 containing the transient receptor potential cation channel, subfamily V, members 5 (Trpv5 and 6 (Trpv6 genes. DNA sequence analysis of coding regions, intron-exon boundaries and promoters of Trpv5 and Trpv6 identified a novel T to C transition in codon 682 of TRPV5, mutating a conserved serine to a proline (S682P. Compared to wild-type littermates, heterozygous (Trpv5(682P/+ and homozygous (Trpv5(682P/682P mutant mice had hypercalciuria, polyuria, hyperphosphaturia and a more acidic urine, and ∼10% of males developed tubulointerstitial nephritis. Trpv5(682P/682P mice also had normal plasma parathyroid hormone but increased 1,25-dihydroxyvitamin D(3 concentrations without increased bone resorption, consistent with a renal defect for the hypercalciuria. Expression of the S682P mutation in human embryonic kidney cells revealed that TRPV5-S682P-expressing cells had a lower baseline intracellular calcium concentration than wild-type TRPV5-expressing cells, suggesting an altered calcium permeability. Immunohistological studies revealed a selective decrease in TRPV5-expression from the renal distal convoluted tubules of Trpv5(682P/+ and Trpv5(682P/682P mice consistent with a trafficking defect. In addition, Trpv5(682P/682P mice had a reduction in renal expression of the intracellular calcium-binding protein, calbindin-D(28K, consistent with a specific defect in TRPV5-mediated renal calcium reabsorption. Thus, our findings

  20. Coregulation of calcium channels and beta-adrenergic receptors in cultured chick embryo ventricular cells

    International Nuclear Information System (INIS)

    To examine mechanisms whereby the abundance of functional Ca channels may be regulated in excitable tissue, Ca channel number was estimated by binding of the dihydropyridine (DHP) antagonist 3H (+)PN200-110 to monolayers of intact myocytes from chick embryo ventricle. Beta adrenergic receptor properties were studied in cultured myocytes using [3H]CGP12177, an antagonist ligand. Physiological correlates for alterations in DHP binding site number included 45Ca uptake and contractile response to (+)BAYk 8644, a specific L-type Ca channel activator. All binding and physiological determinations were performed in similar intact cell preparations under identical conditions. 4-h exposure to 1 microM isoproterenol reduced cell surface beta-adrenergic receptor number from 44 +/- 3 to 17 +/- 2 fmol/mg (P less than 0.05); DHP binding sites declined in number from 113 +/- 25 to 73 +/- 30 fmol/mg (P less than 0.03). When protein kinase A was activated by a non-receptor-dependent mechanism, DHP binding declined similarly to 68% of control. Exposure to diltiazem, a Ca channel antagonist, for 18-24 h had no effect on number of DHP binding sites. After 4-h isoproterenol exposure, 45Ca uptake stimulated by BAYk 8644 declined from 3.3 +/- 0.2 nmol/mg to 2.9 +/- 0.3 nmol/mg (P less than 0.01) and BAYk 8644-stimulated increase in amplitude of contraction declined from 168 +/- 7 to 134 +/- 11% (P = 0.02). Thus, elevation of [cAMP] in myocytes is associated with a time-dependent decline in Ca channel abundance as estimated by DHP binding and a decline in physiological responses that are in part dependent on abundance of Ca channels. Binding of a directly acting Ca channel antagonist for 18-24 h does not modulate the number of DHP binding sites

  1. Endo-lysosomal TRP mucolipin-1 channels trigger global ER Ca2+ release and Ca2+ influx

    Science.gov (United States)

    Kilpatrick, Bethan S.; Yates, Elizabeth; Grimm, Christian; Schapira, Anthony H.

    2016-01-01

    ABSTRACT Transient receptor potential (TRP) mucolipins (TRPMLs), encoded by the MCOLN genes, are patho-physiologically relevant endo-lysosomal ion channels crucial for membrane trafficking. Several lines of evidence suggest that TRPMLs mediate localised Ca2+ release but their role in Ca2+ signalling is not clear. Here, we show that activation of endogenous and recombinant TRPMLs with synthetic agonists evoked global Ca2+ signals in human cells. These signals were blocked by a dominant-negative TRPML1 construct and a TRPML antagonist. We further show that, despite a predominant lysosomal localisation, TRPML1 supports both Ca2+ release and Ca2+ entry. Ca2+ release required lysosomal and ER Ca2+ stores suggesting that TRPMLs, like other endo-lysosomal Ca2+ channels, are capable of ‘chatter’ with ER Ca2+ channels. Our data identify new modalities for TRPML1 action. PMID:27577094

  2. Selective modulation of cellular voltage dependent calcium channels by hyperbaric pressure - a suggested HPNS partial mechanism

    Directory of Open Access Journals (Sweden)

    Ben eAviner

    2014-05-01

    Full Text Available Professional deep sea divers experience motor and cognitive impairment, known as High Pressure Neurological Syndrome (HPNS, when exposed to pressures of 100 msw (1.1MPa and above, considered to be the result of synaptic transmission alteration. Previous studies have indicated modulation of presynaptic Ca2+ currents at high pressure. We directly measured for the first time pressure effects on the currents of voltage dependent Ca2+ channels (VDCCs expressed in Xenopus oocytes. Pressure selectivity augmented the current in CaV1.2 and depressed it in CaV3.2 channels. Pressure application also affected the channels' kinetics, such as ƮRise, ƮDecay. Pressure modulation of VDCCs seems to play an important role in generation of HPNS signs and symptoms.

  3. Release of intracellular Calcium increase production of mitochondrial reactive oxygen species in renal distal epithelial cells

    DEFF Research Database (Denmark)

    Bjerregaard, Henning F.

    was inhibited by buffering of intracellular calcium with BAPTA, by the antioxidant N-acetylcysteine and by uncoupling of mitochondrial oxidative phosphorylation from respiration with CCCP. These results indicate that Cd generate a prompt initiation of ROS production from mitochondria due to an increase...... peroxide (H2O2) has traditionally been regarded as toxic by-products of aerobic metabolism. However, recent findings indicate that H2O2 act as a signalling molecule. The aim of the present study was to monitor, in real time, the rates of ROS generation in order to directly determine their production...

  4. Effects of Calcium-Channel Noise on Dynamics of Excitation-Contraction Coupling in Paced Cardiac Cells

    Directory of Open Access Journals (Sweden)

    Jiying Ma

    2013-01-01

    Full Text Available We study a simple discrete model with the impact of calcium-channel noise on the beat-to-beat dynamics of cardiac cells. The effects of the noise are assessed by bifurcation analysis and power spectrum analysis, respectively. It is shown that this model can undergo period-doubling bifurcation and Hopf bifurcation if there are not random perturbations. Under random perturbations, the period-doubling bifurcations of the model can be observed, and the invariant curve from Hopf bifurcation is perturbed to an annulus on the plane and then becomes a totally disordered and randomly scattered region. By the power spectrum analysis, we find that the existence of high-frequency peak in the power spectra links to the period-doubling orbits, while the existence of low-frequency peak corresponds to quasiperiodic orbit.

  5. The use of [11C]diazomethane for labelling a calcium channel antagonist: PN 200-110 (Isrodipine)

    International Nuclear Information System (INIS)

    PN 200-110 (Isrodipine), a calcium channel antagonist, was labelled with 11C (t1/2 20.4 min) by a reaction between [11C]diazomethane and the carboxyl precursor. The [11C]CH2N2 is prepared in two stages from [11C]CH4: [11C]CH4→[11C]CHCl3→[11C]CH2N2. When a mixture of nitrogen (95%) and hydrogen (5%) is irradiated with 20 MeV protons (30 min, 30 μ A), 60-80 mCi of product are prepared and purified with HPLC. The 11C product is ready for medical use within 35 min of the end of bombardment. (author)

  6. Calcium-channel blockers do not alter the clinical efficacy of clopidogrel after myocardial infarction: a nationwide cohort study

    DEFF Research Database (Denmark)

    Olesen, Jonas B; Gislason, Gunnar H; Charlot, Mette G;

    2011-01-01

    Objectives The purpose of this study was to determine the risk of adverse cardiovascular events associated with concomitant use of clopidogrel and calcium-channel blockers (CCBs) in patients with myocardial infarction (MI). Background CCBs inhibit a variety of cytochrome P-450 enzymes, some....... The cohort was divided into patients treated with and without clopidogrel and followed for 1 year after discharge. The risk of a composite of cardiovascular death, MI, or stroke and the risk of the individual components of the composite end point and all-cause death associated with CCBs were analyzed...... adverse end points and propensity score–matched models provided similar results. Conclusions The clinical efficacy of clopidogrel in patients with a recent MI is not modified by concomitant CCB treatment. This potential drug interaction is unlikely to have clinical significance....

  7. Inhibition of voltage-gated calcium channels as common mode of action for (mixtures of) distinct classes of insecticides.

    Science.gov (United States)

    Meijer, Marieke; Dingemans, Milou M L; van den Berg, Martin; Westerink, Remco H S

    2014-09-01

    Humans are exposed to distinct structural classes of insecticides with different neurotoxic modes of action. Because calcium homeostasis is essential for proper neuronal function and development, we investigated the effects of insecticides from different classes (pyrethroid: (α-)cypermethrin; organophosphate: chlorpyrifos; organochlorine: endosulfan; neonicotinoid: imidacloprid) and mixtures thereof on the intracellular calcium concentration ([Ca(2+)]i). Effects of acute (20 min) exposure to (mixtures of) insecticides on basal and depolarization-evoked [Ca(2+)]i were studied in vitro with Fura-2-loaded PC12 cells and high resolution single-cell fluorescence microscopy. The data demonstrate that cypermethrin, α-cypermethrin, endosulfan, and chlorpyrifos concentration-dependently decreased depolarization-evoked [Ca(2+)]i, with 50% (IC50) at 78nM, 239nM, 250nM, and 899nM, respectively. Additionally, acute exposure to chlorpyrifos or endosulfan (10μM) induced a modest increase in basal [Ca(2+)]i, amounting to 68 ± 8nM and 53 ± 8nM, respectively. Imidacloprid did not disturb basal or depolarization-evoked [Ca(2+)]i at 10μM. Following exposure to binary mixtures, effects on depolarization-evoked [Ca(2+)]i were within the expected effect additivity range, whereas the effect of the tertiary mixture was less than this expected additivity effect range. These results demonstrate that different types of insecticides inhibit depolarization-evoked [Ca(2+)]i in PC12 cells by inhibiting voltage-gated calcium channels (VGCCs) in vitro at concentrations comparable with human occupational exposure levels. Moreover, the effective concentrations in this study are below those for earlier described modes of action. Because inhibition of VGCCs appears to be a common and potentially additive mode of action of several classes of insecticides, this target should be considered in neurotoxicity risk assessment studies.

  8. Mechanism of inhibition of calcium channels in rat nucleus tractus solitarius by neurotransmitters.

    OpenAIRE

    Rhim, H; Toth, P. T.; Miller, R. J.

    1996-01-01

    1. High-threshold Ca2+ channel currents were measured every 15 s following a 200 ms voltage step from -80 mV to 0 mV in order to study the coupling mechanism between neurotransmitter receptors and Ca2+ channels in neurones acutely isolated from the nucleus tractus solitarius (NTS) of the rat. 2. Application of 30 microM baclofen (GABAB receptor agonist) caused 38.9 +/- 1.2% inhibition of the peak inward Ba2+ current (IBa2+) in most NTS cells tested (n = 85 of 88). Somatostatin, 300 nM, also r...

  9. In vitro study of vancomycin release and osteoblast-like cell growth on structured calcium phosphate-collagen

    Energy Technology Data Exchange (ETDEWEB)

    Pon-On, Weeraphat, E-mail: wponun@yahoo.com [Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Charoenphandhu, Narattaphol; Teerapornpuntakit, Jarinthorn; Thongbunchoo, Jirawan; Krishnamra, Nateetip [Center of Calcium and Bone Research, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Department of Physiology, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Tang, I-Ming [ThEP Center, Commission of Higher Education. 328 Si Ayuthaya Rd., Bangkok 10400 (Thailand); Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand)

    2013-04-01

    A drug delivery vehicle consisting of spherical calcium phosphate-collagen particles covered by flower-like (SFCaPCol) blossoms composed of nanorod building blocks and their cellular response is studied. The spherical structure was achieved by a combination of sonication and freeze-drying. The SFCaPCol blossoms have a high surface area of approximately 280 m{sup 2}g{sup −1}. The blossom-like formation having a high surface area allows a drug loading efficiency of 77.82%. The release profile for one drug, vancomycin (VCM), shows long term sustained release in simulated body fluid (SBF), in a phosphate buffer saline (PBS, pH 7.4) solution and in culture media over 2 weeks with a cumulative release ∼ 53%, 75% and 50%, respectively, over the first 7 days. The biocompatibility of the VCM-loaded SFCaPCol scaffold was determined by in vitro cell adhesion and proliferation tests of rat osteoblast-like UMR-106 cells. MTT tests indicated that UMR-106 cells were viable after exposure to the VCM loaded SFCaPCol, meaning that the scaffold (the flower-like blossoms) did not impair the cell's viability. The density of cells on the substrate was seen to increase with increasing cultured time. - Graphical abstract: A spherical calcium phosphate-collagen with flower-like blossoms consisting of nanorod building blocks (SFCaPCol) particles was achieved by a combination of sonication and freeze-drying. In vitro drug release profile and the biocompatibility of the VCM-loaded SFCaPCol composite cell adhesion and proliferation in rat osteoblast-like UMR-106 cells were determined for biomaterial applications. Highlights: ► SFCaPCol and VCM-loaded SFCaPCol composite were synthesized by a combination of ultra sonication and freeze-drying. ► VCM drug-loaded SFCaPCol composite was used as substrate for the growth of rat osteoblast-like UMR-106 cells. ► Controlled release of VCM from the composite is critically medium dependent. ► The VCM-loaded SFCaPCol composite is also

  10. Stretch induced endothelin-1 secretion by adult rat astrocytes involves calcium influx via stretch-activated ion channels (SACs)

    International Nuclear Information System (INIS)

    Highlights: → Endothelin-1 expression by adult rat astrocytes correlates with cell proliferation. → Stretch-induced ET-1 is inhibited by GsMtx-4, a specific inhibitor of Ca2+ permeant SACs. → The less specific SAC inhibitor streptomycin also inhibits ET-1 secretion. → Stretch-induced ET-1 production depends on a calcium influx. → SAC pharmacology may provide a new class of therapeutic agents for CNS pathology. -- Abstract: The expression of endothelins (ETs) and ET-receptors is often upregulated in brain pathology. ET-1, a potent vasoconstrictor, also inhibits the expression of astrocyte glutamate transporters and is mitogenic for astrocytes, glioma cells, neurons, and brain capillary endothelia. We have previously shown that mechanical stress stimulates ET-1 production by adult rat astrocytes. We now show in adult astrocytes that ET-1 production is driven by calcium influx through stretch-activated ion channels (SACs) and the ET-1 production correlates with cell proliferation. Mechanical stimulation using biaxial stretch (2+ threshold. This coupling of mechanical stress to the astrocyte endothelin system through SACs has treatment implications, since all pathology deforms the surrounding parenchyma.

  11. Dose calcium channel blocker verapamil decrease urinary VMA levels in sympathoadrenal hyperactive patients with posttraumatic stress disorder?

    Institute of Scientific and Technical Information of China (English)

    Munawar Alam Ansari; Shahida PAhmed; Zahida Memon

    2008-01-01

    Objective:The majority of the patients with posttraumatic stress disorders (PTSD)embrace augmented urina-ry flow of Vanillylmandelic Acid (VMA)than normal subjects owing to superior sympathetic doings,which steer to cardiovascular catastrophe.Urinary flow of VMA was evaluated as sympathoadrenal bustle marker in patients with posttraumatic stress disorder.Calcium ion shows a noteworthy dependability in nervousness owing to its special effects on brain synaptosomes.So this study was conducted to explore the effects of Verapamil on sympathoadrenal motion in patients with PTSD.Methods:Placebo controlled clinical tryout was conducted. At first hundred (100)PTSD patients were chosen and enrolled in the study,from department of Psychological Medicine Dow University of Health Sciences,Karachi.Verapamil 120 mg/day was specified in divided doses to group-I (n =50)patients and group-II (n =50)patients received placebo therapy on a daily basis for nine weeks.Each and every patient was monitored weekly,all the way through extent of study.Results:Under-neath the posttraumatic stress disorder,urinary excretion of VMA was greater.Calcium channel blocker vera-pamil additionally abolished the embellished retort in urinary flow of VMA appreciably in patients with PTSD. Conclusion:Verapamil was experiential to be exceedingly effectual treatment.It reduces VMA levels in u-rine,and on the whole cardiovascular threat in PTSD patients.

  12. Effects and mechanisms of store-operated calcium channel blockade on hepatic ischemia-reperfusion injury in rats

    Institute of Scientific and Technical Information of China (English)

    Li-Jie Pan; Zi-Chao Zhang; Zhen-Ya Zhang; Wen-Jun Wang; Yue Xu; Zong-Ming Zhang

    2012-01-01

    AIM: To further investigate the important role of storeoperated calcium channels (SOCs) in rat hepatocytes and to explore the effects of SOC blockers on hepatic ischemia-reperfusion injury (HIRI). METHODS: Using freshly isolated hepatocytes from a rat model of HIRI (and controls), we measured cytosolic free Ca2+ concentration (by calcium imaging), net Ca2+ fluxes (by a non-invasive micro-test technique), the SOC current (ISOC; by whole-cell patch-clamp recording), and taurocholate secretion [by high-performance liquid chromatography and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays]. RESULTS: Ca2+ oscillations and net Ca2+ fluxes mediated by Ca2+ entry via SOCs were observed in rat hepatocytes. ISOC was significantly higher in HIRI groups than in controls (57.0 ± 7.5 pA vs 31.6 ± 2.7 pA, P <0.05) and was inhibited by La3+. Taurocholate secretion by hepatocytes into culture supernatant was distinctly lower in HIRI hepatocytes than in controls, an effect reversed by SOC blockers. CONCLUSION: SOCs are pivotal in HIRI. SOC blockers protected against HIRI and assisted the recovery of secretory function in hepatocytes. Thus, they are likely to become a novel class of effective drugs for prevention or therapy of HIRI patients in the future.

  13. [3H]TA-3090, a selective benzothiazepine-type calcium channel receptor antagonist: In vitro characterization

    International Nuclear Information System (INIS)

    Binding of the new benzothiazepine calcium channel blocker, (+)-(2S,3S)-3-acetoxy-8-chloro-5-(2-(dimethylamino)ethyl)-2,3-dihydro-2- (4- methoxyphenyl)-1,5-benzothiazepine-4-(5H)-one maleate, [3H]TA-3090, was characterized and its specificity for rat myocardial benzothiazepine receptors described. Scatchard plots and nonlinear regression analysis of specific [3H]TA-3090 binding best fit a one-site binding model (Kd = 8.8 +/- 2.7 nM, Bmax = 132 +/- 38 fmol/mg protein). Kinetically derived affinity constants were in close agreement (Kd = 7.86 nM) with those obtained from analysis of equilibrium binding data. In comparison, under identical conditions [3H]diltiazem exhibited a Kd of 38 nM and Bmax, 106 fmol/mg protein. Specific binding was saturable, reversible and stereoselective (d-cis-TA-3090 Ki = 14 nM; 1-cis-TA-3090 Ki = 2700 nM). Competitions for [3H]TA-3090 binding were conducted with nifedipine, propranolol, prazosin, quinuclidinyl benzilate, verapamil and yohimbine. Only the calcium channel blockers nifedipine and verapamil inhibited specific [3H]TA-3090 binding. Nifedipine could maximally inhibit only 52% of specifically bound [3H]TA-3090 at 10 microM. In contrast, however, 10 microM verapamil completely inhibited specific radioligand binding (Ki = 93 +/- 28 nM) but with six times less efficacy than TA-3090. Thus, these data demonstrate that [3H]TA-3090 is a potent radioligand selective for the benzothiazepine binding site and is consistent with the hypothesis that [3H]TA-3090 interacts with a myocardial benzothiazepine receptor site

  14. Cardioprotective effect of an L/N-type calcium channel blocker in patients with hypertensive heart disease

    International Nuclear Information System (INIS)

    Left ventricular (LV) diastolic dysfunction is related to increased cardiac sympathetic activity. We investigated the effect of cilnidipine, an L/N-type calcium channel blocker, on LV diastolic function and cardiac sympathetic activity in patients with hypertensive heart disease (HHD) using radionuclide myocardial imaging. Thirty-two frame electrocardiography (ECG)-gated 99mTc-sestamibi (MIBI) myocardial single photon emission computed tomography (SPECT), and 123I-metaiodobenzylguanidine (MIBG) imaging were performed before and 6 months after drug administration in 32 outpatients with HHD. Sixteen of the patients were treated with cilnidipine and the other 16 were treated with nifedipine retard. The parameters for assessing LV diastolic function evaluated using ECG-gated 99mTc-MIBI SPECT were peak filling rate (PFR), first-third filling rate (1/3FR), and time to peak filling (TPF). Cardiac sympathetic activity was assessed as early and delayed heart to mediastinum (H/M) ratios and a washout rate (WR), using 123I-MIBG imaging. The PFR and 1/3FR significantly increased after 6 months of treatment with cilnidipine (p<0.05 for both), but did not with nifedipine retard. The H/M ratios significantly increased (p<0.05 for both) in conjunction with a decreased WR (p<0.05) in the cilnidipine group. Moreover, a significant positive correlation was seen between the rate of change in PFR and the rate of change in early and delayed H/M ratios in the cilnidipine group (p<0.05 for both). The same results were obtained for the relationship between the rate of change in 1/3FR and the rate of change in H/M ratios (p<0.05 for both). However, no such relationship was seen in the nifedipine group. These data indicate that cilnidipine seems to suppress cardiac sympathetic overactivity via blockade of N-type calcium channels and improves LV diastolic function in patients with HHD. (author)

  15. Calcium channel blockers ameliorate iron overload-associated hepatic fibrosis by altering iron transport and stellate cell apoptosis.

    Science.gov (United States)

    Zhang, Ying; Zhao, Xin; Chang, Yanzhong; Zhang, Yuanyuan; Chu, Xi; Zhang, Xuan; Liu, Zhenyi; Guo, Hui; Wang, Na; Gao, Yonggang; Zhang, Jianping; Chu, Li

    2016-06-15

    Liver fibrosis is the principal cause of morbidity and mortality in patients with iron overload. Calcium channel blockers (CCBs) can antagonize divalent cation entry into renal and myocardial cells and inhibit fibrogenic gene expression. We investigated the potential of CCBs to resolve iron overload-associated hepatic fibrosis. Kunming mice were assigned to nine groups (n=8 per group): control, iron overload, deferoxamine, high and low dose verapamil, high and low dose nimodipine, and high and low dose diltiazem. Iron deposition and hepatic fibrosis were measured in mouse livers. Expression levels of molecules associated with transmembrane iron transport were determined by molecular biology approaches. In vitro HSC-T6 cells were randomized into nine groups (the same groups as the mice). Changes in proliferation, apoptosis, and metalloproteinase expression in cells were detected to assess the anti-fibrotic effects of CCBs during iron overload conditions. We found that CCBs reduced hepatic iron content, intracellular iron deposition, the number of hepatic fibrotic areas, collagen expression levels, and hydroxyproline content. CCBs rescued abnormal expression of α1C protein in L-type voltage-dependent calcium channel (LVDCC) and down-regulated divalent metal transporter-1 (DMT-1) expression in mouse livers. In iron-overloaded HSC-T6 cells, CCBs reduced iron deposition, inhibited proliferation, induced apoptosis, and elevated expression of matrix metalloproteinase-13 (MMP-13) and tissue inhibitor of metalloproteinase-1 (TIMP-1). CCBs are potential therapeutic agents that can be used to address hepatic fibrosis during iron overload. They resolve hepatic fibrosis probably correlated with regulating transmembrane iron transport and inhibiting HSC growth. PMID:27095094

  16. INVESTIGATION OF SEIZURE ACTIVITY AFTER CYCLIC NUCLEOTIDE PHOSPHODIESTERASE INHIBITION WITH SECOND MESSENGER AND CALCIUM ION CHANNEL INHIBITION IN MICE

    Directory of Open Access Journals (Sweden)

    J Nandhakumar

    2012-03-01

    Full Text Available The role of PDE-4 inhibitor etazolate, was evaluated in the presence of PDE-7 inhibitor, BRL-50481, in animal models of epilepsy. Seizures were induced in the animals by subjecting them to injection of chemical convulsants, Pilocarpine, Kainic acid (KA and maximal electroshock (MES. The combination of etazolate and BRL50481 treated mice showed a significant (P<0.001 quick onset of action, jerky movements and convulsion when compared to gabapentin. The combination of etazolate and sGC inhibitor, methylene blue (MB treated mice showed a significant (P<0.001 delay in onset of action, jerky movements and convulsion when compare to gabapentin as well as against the combination of etazolate with BRL 50481.The present study mainly highlights the individual effects of etazolate and combination with BRL-50481 potentiates (P<0.001 the onset of seizure activity against all models of convulsion. The study mainly comprises the onset of seizures, mortality/recovery, percentage of prevention of seizures (anticonvulsant and total duration of convulsive time. The total convulsive time was prolonged significantly (P<0.05 and P<0.01 in combination of methylene blue with etazolate treated (28.59% and 35.15 % groups, compared to DMSO received group (100% in the MES model. In the same way, the combination of calcium channel modulator (CCM and calcium channel blocker (CCB amiodarone and nifedipine respectively, with etazolate showed a significant (P<0.001 delay in onset of seizures, compared to DMSO and etazolate treated groups in all models of epilepsy. This confirms that both CCM and CCB possess anticonvulsant activity. Finally, the study reveals that identification of new cAMP mediated phosphodiesterases family members offers a potential new therapy for epilepsy management in future.

  17. N- and L-Type Voltage-Gated Calcium Channels Mediate Fast Calcium Transients in Axonal Shafts of Mouse Peripheral Nerve.

    Science.gov (United States)

    Barzan, Ruxandra; Pfeiffer, Friederike; Kukley, Maria

    2016-01-01

    In the peripheral nervous system (PNS) a vast number of axons are accommodated within fiber bundles that constitute peripheral nerves. A major function of peripheral axons is to propagate action potentials along their length, and hence they are equipped with Na(+) and K(+) channels, which ensure successful generation, conduction and termination of each action potential. However little is known about Ca(2+) ion channels expressed along peripheral axons and their possible functional significance. The goal of the present study was to test whether voltage-gated Ca(2+) channels (VGCCs) are present along peripheral nerve axons in situ and mediate rapid activity-dependent Ca(2+) elevations under physiological circumstances. To address this question we used mouse sciatic nerve slices, Ca(2+) indicator Oregon Green BAPTA-1, and 2-photon Ca(2+) imaging in fast line scan mode (500 Hz). We report that transient increases in intra-axonal Ca(2+) concentration take place along peripheral nerve axons in situ when axons are stimulated electrically with single pulses. Furthermore, we show for the first time that Ca(2+) transients in peripheral nerves are fast, i.e., occur in a millisecond time-domain. Combining Ca(2+) imaging and pharmacology with specific blockers of different VGCCs subtypes we demonstrate that Ca(2+) transients in peripheral nerves are mediated mainly by N-type and L-type VGCCs. Discovery of fast Ca(2+) entry into the axonal shafts through VGCCs in peripheral nerves suggests that Ca(2+) may be involved in regulation of action potential propagation and/or properties in this system, or mediate neurotransmitter release along peripheral axons as it occurs in the optic nerve and white matter of the central nervous system (CNS).

  18. Dissolving behavior and calcium release from fibrous wollastonite in acetic acid solution

    International Nuclear Information System (INIS)

    The degradability of fibrous wollastonite (CaSiO3) in an aqueous solution of acetic acid and leaching of Ca2+ ions were investigated in the temperature range from 22 to 50 oC. The Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES) was used for the assessment of calcium and other selected cations in the leaching medium. The amount of calcium in the solvent can be significantly enhanced through leaching at higher temperature. Fibrous silica particles are the main by-product of the leaching process. The properties of by-product were examined by thermal analysis (simultaneous TG-DTA-EGA), infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The formation of silica layer on the surface of fibrous wollastonite particles is an important factor in the leaching process. Particles were covered by the silica layer and wollastonite core size was continually decreasing during leaching. The shape of resulting silica particles shows no significant changes during this process. Specific surface of the formed fibrous silica particles strongly depends on the leaching temperature.

  19. Pectin/anhydrous dibasic calcium phosphate matrix tablets for in vitro controlled release of water-soluble drug.

    Science.gov (United States)

    Mamani, Pseidy Luz; Ruiz-Caro, Roberto; Veiga, María Dolores

    2015-10-15

    Different pectin/anhydrous dibasic calcium phosphate (ADCP) matrix tablets have been developed in order to obtain controlled release of a water-soluble drug (theophylline). Swelling, buoyancy and dissolution studies have been carried out in different aqueous media (demineralized water, progressive pH medium, simulated gastric fluid, simulated intestinal fluid and simulated colonic fluid), to characterize the matrix tablets. When the pectin/ADCP ratio was ≥0.26 (P1, P2, P3 and P4 tablets) a continuous swelling and low theophylline dissolution rate from the matrices were observed. So, pectin gel forming feature predominated over the ADCP properties, yielding pH-independent drug release behavior from these matrices. On the contrary, pectin/ADCP ratios ≤0.11 (P5 and P6 tablets) allowed to achieve drug dissolution pH dependent. Consequently, the suitable selection of the pectin/ADCP ratio will allow to tailor matrix tablets for controlled release of water-soluble drugs in a specific manner in the gastrointestinal tract. PMID:26276258

  20. Specific inhibition of long-lasting, L-type calcium channels by synthetic parathyroid hormone

    International Nuclear Information System (INIS)

    The effect of an active synthetic N-terminal fragment of bovine parathyroid hormone (bPTH), bPTH-(1-34), on Ca2+ channels was studied in mouse neuroblastoma cells (N1E-115). With the whole-cell variation of the patch-clamp technique, T (transient) and L (long-lasting) types of Ca2+ currents were identified. Pharmacological characterization showed that the L current was amplified by the Ca2+ channel stimulator BAY K-8644, but the T current was unaffected. The administration of bPTH-(1-34) produced dose-related inhibition of the L current, which could be reversed by BAY K-8644. The peptide had no effect on the T current. In addition, use of the fluorescent indicator fura-2 showed that bPTH-(1-34) inhibited the KCl-stimulated increase in intracellular free Ca2+ in neuroblastoma cells with L channels but not in cells with T channels. An inactivated (oxidized) preparation of bPTH-(1-34) failed to affect the L current. High-affinity binding of labeled PTH analog to these neuroblastoma cells was also demonstrated. In addition, bPTH-(1-34) inhibited the L current in cultured vascular smooth muscle cells from rat tail artery. These data indicate that, in some tissues PTH can act as an endogenous blocker of Ca2+ entry

  1. Antibodies to voltage-gated potassium and calcium channels in epilepsy.

    NARCIS (Netherlands)

    Majoie, H.J.; Baets, M.H.V. de; Renier, W.O.; Lang, B.; Vincent, A.

    2006-01-01

    OBJECTIVE: To determine the prevalence of antibodies to ion channels in patients with long standing epilepsy. BACKGROUND: Although the CNS is thought to be protected from circulating antibodies by the blood brain barrier, glutamate receptor antibodies have been reported in Rasmussen's encephalitis,

  2. Expression of calcium-activated chloride channels Ano1 and Ano2 in mouse taste cells.

    Science.gov (United States)

    Cherkashin, Alexander P; Kolesnikova, Alisa S; Tarasov, Michail V; Romanov, Roman A; Rogachevskaja, Olga A; Bystrova, Marina F; Kolesnikov, Stanislav S

    2016-02-01

    Specialized Ca(2+)-dependent ion channels ubiquitously couple intracellular Ca(2+) signals to a change in cell polarization. The existing physiological evidence suggests that Ca(2+)-activated Cl(-) channels (CaCCs) are functional in taste cells. Because Ano1 and Ano2 encode channel proteins that form CaCCs in a variety of cells, we analyzed their expression in mouse taste cells. Transcripts for Ano1 and Ano2 were detected in circumvallate (CV) papillae, and their expression in taste cells was confirmed using immunohistochemistry. When dialyzed with CsCl, taste cells of the type III exhibited no ion currents dependent on cytosolic Ca(2+). Large Ca(2+)-gated currents mediated by TRPM5 were elicited in type II cells by Ca(2+) uncaging. When TRPM5 was inhibited by triphenylphosphine oxide (TPPO), ionomycin stimulated a small but resolvable inward current that was eliminated by anion channel blockers, including T16Ainh-A01 (T16), a specific Ano1 antagonist. This suggests that CaCCs, including Ano1-like channels, are functional in type II cells. In type I cells, CaCCs were prominently active, blockable with the CaCC antagonist CaCCinh-A01 but insensitive to T16. By profiling Ano1 and Ano2 expressions in individual taste cells, we revealed Ano1 transcripts in type II cells only, while Ano2 transcripts were detected in both type I and type II cells. P2Y agonists stimulated Ca(2+)-gated Cl(-) currents in type I cells. Thus, CaCCs, possibly formed by Ano2, serve as effectors downstream of P2Y receptors in type I cells. While the role for TRPM5 in taste transduction is well established, the physiological significance of expression of CaCCs in type II cells remains to be elucidated.

  3. Expression of calcium-activated chloride channels Ano1 and Ano2 in mouse taste cells.

    Science.gov (United States)

    Cherkashin, Alexander P; Kolesnikova, Alisa S; Tarasov, Michail V; Romanov, Roman A; Rogachevskaja, Olga A; Bystrova, Marina F; Kolesnikov, Stanislav S

    2016-02-01

    Specialized Ca(2+)-dependent ion channels ubiquitously couple intracellular Ca(2+) signals to a change in cell polarization. The existing physiological evidence suggests that Ca(2+)-activated Cl(-) channels (CaCCs) are functional in taste cells. Because Ano1 and Ano2 encode channel proteins that form CaCCs in a variety of cells, we analyzed their expression in mouse taste cells. Transcripts for Ano1 and Ano2 were detected in circumvallate (CV) papillae, and their expression in taste cells was confirmed using immunohistochemistry. When dialyzed with CsCl, taste cells of the type III exhibited no ion currents dependent on cytosolic Ca(2+). Large Ca(2+)-gated currents mediated by TRPM5 were elicited in type II cells by Ca(2+) uncaging. When TRPM5 was inhibited by triphenylphosphine oxide (TPPO), ionomycin stimulated a small but resolvable inward current that was eliminated by anion channel blockers, including T16Ainh-A01 (T16), a specific Ano1 antagonist. This suggests that CaCCs, including Ano1-like channels, are functional in type II cells. In type I cells, CaCCs were prominently active, blockable with the CaCC antagonist CaCCinh-A01 but insensitive to T16. By profiling Ano1 and Ano2 expressions in individual taste cells, we revealed Ano1 transcripts in type II cells only, while Ano2 transcripts were detected in both type I and type II cells. P2Y agonists stimulated Ca(2+)-gated Cl(-) currents in type I cells. Thus, CaCCs, possibly formed by Ano2, serve as effectors downstream of P2Y receptors in type I cells. While the role for TRPM5 in taste transduction is well established, the physiological significance of expression of CaCCs in type II cells remains to be elucidated. PMID:26530828

  4. Nitrogen, phosphorus, potassium, calcium and magnesium release from two compressed fertilizers: column experiments

    OpenAIRE

    M. J. Fernández-Sanjurjo; E. Alvarez-Rodríguez; Núñez-Delgado, A.; M. L. Fernández-Marcos; A. Romar-Gasalla

    2014-01-01

    We used soil columns to study nutrients release from two compressed NPK fertilizers. The columns were filled with soil material from the surface horizon of a granitic soil. Tablets of two slow-release NPK fertilizers (11-18-11 or 8-8-16) were placed into the soil, and then water was percolated through the columns in a saturated regime. Percolates were analyzed for N, P, K, Ca and Mg. These nutrients were also determined in soil and fertilizer tablets at the ...

  5. Nitrogen, phosphorus, potassium, calcium and magnesium release from two compressed fertilizers: column experiments

    OpenAIRE

    M. J. Fernández-Sanjurjo; E. Alvarez-Rodríguez; A. Núñez-Delgado; M. L. Fernández-Marcos; Romar-Gasalla, A.

    2014-01-01

    The objective of this work was to study nutrients release from two compressed nitrogen–potassium–phosphorous (NPK) fertilizers. In the Lourizán Forest Center, tablet-type controlled-release fertilizers (CRF) were prepared by compressing various mixtures of fertilizers without covers or binders. We used soil columns (50 cm long and 7.3 cm inner diameter) that were filled with soil from the surface layer (0–20 cm) of an A horizon corresponding to a Cambic Umbrisol. Tablets of ...

  6. C-A4-03: Risks to the Newborn Associated With In-Utero Exposure to Beta-Blockers and Calcium-Channel Blockers

    OpenAIRE

    Davis, Robert; Andrade, Susan; Rubanowice, David; McPhillips, Heather; Boudreau, Denise; Raebel, Marsha; Smith, David; Ulcickas-Yood, M; Lane, Kim; Varghese, Renny; Platt, Richard

    2010-01-01

    Background: While medication use to manage cardiovascular disease during pregnancy is widespread, data on its safety for the developing infant is scarce. We used population-based data from 5 HMOs to study risks for perinatal complications and congenital defects among infants exposed in-utero to beta -blockers and calcium-channel blockers.

  7. Sequential comparison of therapy with beta-blockers and calcium channel blockers with celiprolol therapy in patients with angina pectoris, hypertension, or both

    NARCIS (Netherlands)

    Cleophas, TJM; Niemeyer, MG; Bernink, PJLM; Zwinderman, KH; Wijk, AV; Wall, EEVD

    1996-01-01

    Unlike patients with either hypertension (HT) of angina pectoris (AP) alone, patients with both HT and AP usually have a reduced left ventricular compliance and may, therefore, have an impaired capability to cope with acute hemodynamic changes generated by standard beta-blockers or calcium channel b

  8. Like Extinction, Latent Inhibition of Conditioned Fear in Mice Is Blocked by Systemic Inhibition of L-Type Voltage-Gated Calcium Channels

    Science.gov (United States)

    Blouin, Ashley M.; Cain, Chris K.; Barad, Mike

    2004-01-01

    Having recently shown that extinction of conditioned fear depends on L-type voltage-gated calcium channels (LVGCCs), we have been seeking other protocols that require this unusual induction mechanism. We tested latent inhibition (LI) of fear, because LI resembles extinction except that cue exposures precede, rather than follow, cue-shock pairing.…

  9. EFFECTS OF PYRETHROIDS ON VOLTAGE-SENSITIVE CALCIUM CHANNELS: A CRITICAL EVALUATION OF STRENGTHS, WEAKNESSES, DATA NEEDS, AND RELATIONSHIP TO ASSESSMENT OF CUMULATIVE NEUROTOXICITY.

    Science.gov (United States)

    A recently published review (Soderlund et al., 2002, Toxicology 171, 3-59.) of the mechanisms of acute neurotoxicity of pyrethroid compounds postulated that voltage-sensitive calcium channels (VSCC) may be a target of some pyrethroid compounds and that effects on VSCC may contrib...

  10. The juvenile myoclonic epilepsy mutant of the calcium channel β(4) subunit displays normal nuclear targeting in nerve and muscle cells.

    Science.gov (United States)

    Etemad, Solmaz; Campiglio, Marta; Obermair, Gerald J; Flucher, Bernhard E

    2014-01-01

    Voltage-gated calcium channels regulate gene expression by controlling calcium entry through the plasma membrane and by direct interactions of channel fragments and auxiliary β subunits with promoters and the epigenetic machinery in the nucleus. Mutations of the calcium channel β(4) subunit gene (CACNB4) cause juvenile myoclonic epilepsy in humans and ataxia and epileptic seizures in mice. Recently a model has been proposed according to which failed nuclear translocation of the truncated β(4) subunit R482X mutation resulted in altered transcriptional regulation and consequently in neurological disease. Here we examined the nuclear targeting properties of the truncated β(4b(1–481)) subunit in tsA-201 cells, skeletal myotubes, and in hippocampal neurons. Contrary to expectation, nuclear targeting of β(4b(1–481)) was not reduced compared with full-length β(4b) in any one of the three cell systems. These findings oppose an essential role of the β(4) distal C-terminus in nuclear targeting and challenge the idea that the nuclear function of calcium channel β(4) subunits is critically involved in the etiology of epilepsy and ataxia in patients and mouse models with mutations in the CACNB4 gene. PMID:24875574

  11. The juvenile myoclonic epilepsy mutant of the calcium channel β4 subunit displays normal nuclear targeting in nerve and muscle cells

    Science.gov (United States)

    Etemad, Solmaz; Campiglio, Marta; Obermair, Gerald J; Flucher, Bernhard E

    2014-01-01

    Voltage-gated calcium channels regulate gene e